diff --git a/bin/verilator b/bin/verilator
index aed3ef2d6..6571d6360 100755
--- a/bin/verilator
+++ b/bin/verilator
@@ -2037,9 +2037,8 @@ This is an example similar to the above, but using SystemC.
       #include "Vour.h"
       int sc_main(int argc, char** argv) {
           Verilated::commandArgs(argc, argv);
-          sc_clock clk("clk", 10, SC_NS, 0.5, 3, SC_NS, true);
-          Vour* top;
-          top = new Vour("top");
+          sc_clock clk{"clk", 10, SC_NS, 0.5, 3, SC_NS, true};
+          Vour* top = new Vour{"top"};
           top->clk(clk);
           while (!Verilated::gotFinish()) { sc_start(1, SC_NS); }
           delete top;
diff --git a/docs/internals.adoc b/docs/internals.adoc
index 0a2f64909..95c712cd0 100644
--- a/docs/internals.adoc
+++ b/docs/internals.adoc
@@ -395,23 +395,19 @@ but is maintained to build successfully with C++14/C++17/C++20.
 We will work with contributors to fix up indentation style issues, but it
 is appreciated if you could match our style:
 
-* All files should contain the magic header to ensure standard indentation:
-+
-   // -*- mode: C++; c-file-style: "cc-mode" -*-
-+
-This sets indentation to the `cc-mode` defaults.  (Verilator predates a
-CC-mode change of several years ago which overrides the defaults with GNU
-style indentation; the `c-set-style` undoes that.)
-
 * Use "mixedCapsSymbols" instead of "underlined_symbols".
 
 * Uas a "p" suffix on variables that are pointers, e.g. "nodep".
 
 * Comment every member variable.
 
-Indentation is automatically maintained with "make format" using
-clang-format version 10.0.0, and yapf for python, and is automatically
-corrected in the CI actions.  For those manually formatting C++ code:
+* In the include directory, use /// to document functions the user calls.
+(This convention has not been applied retroactively.)
+
+C++ and Python indentation is automatically maintained with "make format"
+using clang-format version 10.0.0, and yapf for python, and is
+automatically corrected in the CI actions.  For those manually formatting
+C++ code:
 
 * Use 4 spaces per level, and no tabs.
 
diff --git a/examples/make_hello_sc/sc_main.cpp b/examples/make_hello_sc/sc_main.cpp
index 6fef7ca31..587010712 100644
--- a/examples/make_hello_sc/sc_main.cpp
+++ b/examples/make_hello_sc/sc_main.cpp
@@ -26,7 +26,7 @@ int sc_main(int argc, char* argv[]) {
     if (false && argc && argv) {}
 
     // Construct the Verilated model, from Vtop.h generated from Verilating "top.v"
-    Vtop* top = new Vtop("top");
+    Vtop* top = new Vtop{"top"};
 
     // Initialize SC model
     sc_start(1, SC_NS);
diff --git a/examples/make_tracing_c/sim_main.cpp b/examples/make_tracing_c/sim_main.cpp
index 08fa60098..c38115e2b 100644
--- a/examples/make_tracing_c/sim_main.cpp
+++ b/examples/make_tracing_c/sim_main.cpp
@@ -27,12 +27,15 @@ int main(int argc, char** argv, char** env) {
     // Prevent unused variable warnings
     if (false && argc && argv && env) {}
 
+    // Create logs/ directory in case we have traces to put under it
+    Verilated::mkdir("logs");
+
     // Set debug level, 0 is off, 9 is highest presently used
-    // May be overridden by commandArgs
+    // May be overridden by commandArgs argument parsing
     Verilated::debug(0);
 
     // Randomization reset policy
-    // May be overridden by commandArgs
+    // May be overridden by commandArgs argument parsing
     Verilated::randReset(2);
 
     // Verilator must compute traced signals
@@ -42,14 +45,12 @@ int main(int argc, char** argv, char** env) {
     // This needs to be called before you create any model
     Verilated::commandArgs(argc, argv);
 
-    // Create logs/ directory in case we have traces to put under it
-    Verilated::mkdir("logs");
-
-    // Construct the Verilated model, from Vtop.h generated from Verilating "top.v"
-    // Using unique_ptr is similar to "Vtop* top = new Vtop" then deleting at end
+    // Construct the Verilated model, from Vtop.h generated from Verilating "top.v".
+    // Using unique_ptr is similar to "Vtop* top = new Vtop" then deleting at end.
+    // "TOP" will be the hierarchical name of the module.
     const std::unique_ptr<Vtop> top{new Vtop};
 
-    // Set some inputs
+    // Set Vtop's input signals
     top->reset_l = !0;
     top->clk = 0;
     top->in_small = 1;
@@ -82,7 +83,7 @@ int main(int argc, char** argv, char** env) {
         // Evaluate model
         // (If you have multiple models being simulated in the same
         // timestep then instead of eval(), call eval_step() on each, then
-        // eval_end_step() on each.)
+        // eval_end_step() on each. See the manual.)
         top->eval();
 
         // Read outputs
@@ -95,7 +96,7 @@ int main(int argc, char** argv, char** env) {
     // Final model cleanup
     top->final();
 
-    //  Coverage analysis (since test passed)
+    // Coverage analysis (calling write only after the test is known to pass)
 #if VM_COVERAGE
     Verilated::mkdir("logs");
     VerilatedCov::write("logs/coverage.dat");
diff --git a/examples/make_tracing_sc/sc_main.cpp b/examples/make_tracing_sc/sc_main.cpp
index 4f7628113..ee42a0aa6 100644
--- a/examples/make_tracing_sc/sc_main.cpp
+++ b/examples/make_tracing_sc/sc_main.cpp
@@ -29,21 +29,26 @@ int sc_main(int argc, char* argv[]) {
     // Prevent unused variable warnings
     if (false && argc && argv) {}
 
+    // Create logs/ directory in case we have traces to put under it
+    Verilated::mkdir("logs");
+
     // Set debug level, 0 is off, 9 is highest presently used
-    // May be overridden by commandArgs
+    // May be overridden by commandArgs argument parsing
     Verilated::debug(0);
 
     // Randomization reset policy
-    // May be overridden by commandArgs
+    // May be overridden by commandArgs argument parsing
     Verilated::randReset(2);
 
+#if VM_TRACE
+    // Before any evaluation, need to know to calculate those signals only used for tracing
+    Verilated::traceEverOn(true);
+#endif
+
     // Pass arguments so Verilated code can see them, e.g. $value$plusargs
     // This needs to be called before you create any model
     Verilated::commandArgs(argc, argv);
 
-    // Create logs/ directory in case we have traces to put under it
-    Verilated::mkdir("logs");
-
     // General logfile
     ios::sync_with_stdio();
 
@@ -64,7 +69,7 @@ int sc_main(int argc, char* argv[]) {
     // Using unique_ptr is similar to "Vtop* top = new Vtop" then deleting at end
     const std::unique_ptr<Vtop> top{new Vtop{"top"}};
 
-    // Attach signals to the model
+    // Attach Vtop's signals to this upper model
     top->clk(clk);
     top->fastclk(fastclk);
     top->reset_l(reset_l);
@@ -75,11 +80,6 @@ int sc_main(int argc, char* argv[]) {
     top->out_quad(out_quad);
     top->out_wide(out_wide);
 
-#if VM_TRACE
-    // Before any evaluation, need to know to calculate those signals only used for tracing
-    Verilated::traceEverOn(true);
-#endif
-
     // You must do one evaluation before enabling waves, in order to allow
     // SystemC to interconnect everything for testing.
     sc_start(1, SC_NS);
@@ -128,7 +128,7 @@ int sc_main(int argc, char* argv[]) {
     }
 #endif
 
-    //  Coverage analysis (since test passed)
+    // Coverage analysis (calling write only after the test is known to pass)
 #if VM_COVERAGE
     Verilated::mkdir("logs");
     VerilatedCov::write("logs/coverage.dat");
diff --git a/include/verilated.h b/include/verilated.h
index 9e2ab1059..1543a4223 100644
--- a/include/verilated.h
+++ b/include/verilated.h
@@ -122,7 +122,7 @@ enum VerilatedVarFlags {
 };
 
 //=========================================================================
-/// Mutex and threading support
+// Mutex and threading support
 
 /// Return current thread ID (or 0), not super fast, cache if needed
 extern vluint32_t VL_THREAD_ID() VL_MT_SAFE;
@@ -135,7 +135,9 @@ extern vluint32_t VL_THREAD_ID() VL_MT_SAFE;
 class VL_CAPABILITY("mutex") VerilatedMutex final {
 private:
     std::mutex m_mutex;  // Mutex
+
 public:
+    /// Construct mutex (without locking it)
     VerilatedMutex() = default;
     ~VerilatedMutex() = default;
     const VerilatedMutex& operator!() const { return *this; }  // For -fthread_safety
@@ -165,25 +167,29 @@ private:
     VerilatedMutex& m_mutexr;
 
 public:
+    /// Construct and hold given mutex lock until destruction or unlock()
     explicit VerilatedLockGuard(VerilatedMutex& mutexr) VL_ACQUIRE(mutexr)
         : m_mutexr(mutexr) {  // Need () or GCC 4.8 false warning
         m_mutexr.lock();
     }
+    /// Destruct and unlock the mutex
     ~VerilatedLockGuard() VL_RELEASE() { m_mutexr.unlock(); }
+    /// Unlock the mutex
     void lock() VL_ACQUIRE() { m_mutexr.lock(); }
+    /// Lock the mutex
     void unlock() VL_RELEASE() { m_mutexr.unlock(); }
 };
 
 #else  // !VL_THREADED
 
-/// Empty non-threaded mutex to avoid #ifdefs in consuming code
+// Empty non-threaded mutex to avoid #ifdefs in consuming code
 class VerilatedMutex final {
 public:
     void lock() {}
     void unlock() {}
 };
 
-/// Empty non-threaded lock guard to avoid #ifdefs in consuming code
+// Empty non-threaded lock guard to avoid #ifdefs in consuming code
 class VerilatedLockGuard final {
     VL_UNCOPYABLE(VerilatedLockGuard);
 
@@ -196,20 +202,22 @@ public:
 
 #endif  // VL_THREADED
 
-/// Remember the calling thread at construction time, and make sure later calls use same thread
+// Internals: Remember the calling thread at construction time, and make
+// sure later calls use same thread
+
 class VerilatedAssertOneThread final {
     // MEMBERS
 #if defined(VL_THREADED) && defined(VL_DEBUG)
     vluint32_t m_threadid;  /// Thread that is legal
 public:
     // CONSTRUCTORS
-    /// The constructor establishes the thread id for all later calls.
-    /// If necessary, a different class could be made that inits it otherwise.
+    // The constructor establishes the thread id for all later calls.
+    // If necessary, a different class could be made that inits it otherwise.
     VerilatedAssertOneThread()
         : m_threadid{VL_THREAD_ID()} {}
     ~VerilatedAssertOneThread() { check(); }
     // METHODS
-    /// Check that the current thread ID is the same as the construction thread ID
+    // Check that the current thread ID is the same as the construction thread ID
     void check() VL_MT_UNSAFE_ONE {
         if (VL_UNCOVERABLE(m_threadid != VL_THREAD_ID())) {
             if (m_threadid == 0) {
@@ -495,16 +503,20 @@ public:
     static const char* profThreadsFilenamep() VL_MT_SAFE { return s_ns.s_profThreadsFilenamep; }
 
     typedef void (*VoidPCb)(void*);  // Callback type for below
-    /// Callbacks to run on global flush
+    /// Add callback to run on global flush
     static void addFlushCb(VoidPCb cb, void* datap) VL_MT_SAFE;
+    /// Remove callback to run on global flush
     static void removeFlushCb(VoidPCb cb, void* datap) VL_MT_SAFE;
+    /// Run flush callbacks registered with addFlushCb
     static void runFlushCallbacks() VL_MT_SAFE;
 #ifndef VL_NO_LEGACY
     static void flushCall() VL_MT_SAFE { runFlushCallbacks(); }  // Deprecated
 #endif
-    /// Callbacks to run prior to termination
+    /// Add callback to run prior to exit termination
     static void addExitCb(VoidPCb cb, void* datap) VL_MT_SAFE;
+    /// Remove callback to run prior to exit termination
     static void removeExitCb(VoidPCb cb, void* datap) VL_MT_SAFE;
+    /// Run exit callbacks registered with addExitCb
     static void runExitCallbacks() VL_MT_SAFE;
 
     /// Record command line arguments, for retrieval by $test$plusargs/$value$plusargs,
@@ -519,11 +531,12 @@ public:
     /// Match plusargs with a given prefix. Returns static char* valid only for a single call
     static const char* commandArgsPlusMatch(const char* prefixp) VL_MT_SAFE;
 
-    /// Produce name & version for (at least) VPI
+    /// Return product name for (at least) VPI
     static const char* productName() VL_PURE;
+    /// Return product version for (at least) VPI
     static const char* productVersion() VL_PURE;
 
-    /// Convenience OS utilities
+    /// Call OS to make a directory
     static void mkdir(const char* dirname) VL_MT_UNSAFE;
 
     /// When multithreaded, quiesce the model to prepare for trace/saves/coverage
@@ -575,17 +588,17 @@ public:
     static size_t serialized2Size() VL_PURE;
     static void* serialized2Ptr() VL_MT_UNSAFE;
 #ifdef VL_THREADED
-    /// Internal: Set the mtaskId, called when an mtask starts
+    // Internal: Set the mtaskId, called when an mtask starts
     static void mtaskId(vluint32_t id) VL_MT_SAFE { t_s.t_mtaskId = id; }
     static vluint32_t mtaskId() VL_MT_SAFE { return t_s.t_mtaskId; }
     static void endOfEvalReqdInc() VL_MT_SAFE { ++t_s.t_endOfEvalReqd; }
     static void endOfEvalReqdDec() VL_MT_SAFE { --t_s.t_endOfEvalReqd; }
 
-    /// Internal: Called at end of each thread mtask, before finishing eval
+    // Internal: Called at end of each thread mtask, before finishing eval
     static void endOfThreadMTask(VerilatedEvalMsgQueue* evalMsgQp) VL_MT_SAFE {
         if (VL_UNLIKELY(t_s.t_endOfEvalReqd)) endOfThreadMTaskGuts(evalMsgQp);
     }
-    /// Internal: Called at end of eval loop
+    // Internal: Called at end of eval loop
     static void endOfEval(VerilatedEvalMsgQueue* evalMsgQp) VL_MT_SAFE;
 #endif
 
@@ -604,7 +617,7 @@ private:
 /// Verilator internal code must call VL_FINISH_MT instead, which eventually calls this.
 extern void vl_finish(const char* filename, int linenum, const char* hier);
 
-/// Routine to call for $stop
+/// Routine to call for $stop and non-fatal error
 /// User code may wish to replace this function, to do so, define VL_USER_STOP.
 /// This code does not have to be thread safe.
 /// Verilator internal code must call VL_FINISH_MT instead, which eventually calls this.
diff --git a/include/verilated_dpi.h b/include/verilated_dpi.h
index 5d666669d..cc2e27ef3 100644
--- a/include/verilated_dpi.h
+++ b/include/verilated_dpi.h
@@ -32,7 +32,7 @@
 //===================================================================
 // SETTING OPERATORS
 
-/// Convert svBitVecVal to Verilator internal data
+// Convert svBitVecVal to Verilator internal data
 static inline void VL_SET_W_SVBV(int obits, WDataOutP owp, const svBitVecVal* lwp) VL_MT_SAFE {
     int words = VL_WORDS_I(obits);
     for (int i = 0; i < words - 1; ++i) owp[i] = lwp[i];
@@ -43,7 +43,7 @@ static inline QData VL_SET_Q_SVBV(const svBitVecVal* lwp) VL_MT_SAFE {
 }
 static inline IData VL_SET_I_SVBV(const svBitVecVal* lwp) VL_MT_SAFE { return lwp[0]; }
 
-/// Convert Verilator internal data to svBitVecVal
+// Convert Verilator internal data to svBitVecVal
 static inline void VL_SET_SVBV_W(int obits, svBitVecVal* owp, WDataInP lwp) VL_MT_SAFE {
     int words = VL_WORDS_I(obits);
     for (int i = 0; i < words - 1; ++i) owp[i] = lwp[i];
@@ -54,8 +54,8 @@ static inline void VL_SET_SVBV_Q(int, svBitVecVal* owp, QData ld) VL_MT_SAFE {
     VL_SET_WQ(owp, ld);
 }
 
-/// Convert svLogicVecVal to Verilator internal data
-/// Note these functions ignore X/Z in svLogicVecVal
+// Convert svLogicVecVal to Verilator internal data
+// Note these functions ignore X/Z in svLogicVecVal
 static inline void VL_SET_W_SVLV(int obits, WDataOutP owp, const svLogicVecVal* lwp) VL_MT_SAFE {
     int words = VL_WORDS_I(obits);
     for (int i = 0; i < words - 1; ++i) owp[i] = lwp[i].aval;
@@ -66,8 +66,8 @@ static inline QData VL_SET_Q_SVLV(const svLogicVecVal* lwp) VL_MT_SAFE {
 }
 static inline IData VL_SET_I_SVLV(const svLogicVecVal* lwp) VL_MT_SAFE { return lwp[0].aval; }
 
-/// Convert Verilator internal data to svLogicVecVal
-/// Note these functions never create X/Z in svLogicVecVal
+// Convert Verilator internal data to svLogicVecVal
+// Note these functions never create X/Z in svLogicVecVal
 static inline void VL_SET_SVLV_W(int obits, svLogicVecVal* owp, WDataInP lwp) VL_MT_SAFE {
     int words = VL_WORDS_I(obits);
     for (int i = 0; i < words; ++i) owp[i].bval = 0;
diff --git a/include/verilated_fst_c.cpp b/include/verilated_fst_c.cpp
index c205ceda8..8842023c0 100644
--- a/include/verilated_fst_c.cpp
+++ b/include/verilated_fst_c.cpp
@@ -15,7 +15,6 @@
 /// \brief C++ Tracing in FST Format
 ///
 //=============================================================================
-// SPDIFF_OFF
 
 // clang-format off
 
diff --git a/include/verilated_fst_c.h b/include/verilated_fst_c.h
index 0e85e1ed1..4c757a816 100644
--- a/include/verilated_fst_c.h
+++ b/include/verilated_fst_c.h
@@ -15,7 +15,6 @@
 /// \brief C++ Tracing in FST Format
 ///
 //=============================================================================
-// SPDIFF_OFF
 
 #ifndef VERILATOR_VERILATED_FST_C_H_
 #define VERILATOR_VERILATED_FST_C_H_
@@ -32,8 +31,8 @@
 
 //=============================================================================
 // VerilatedFst
-/// Base class to create a Verilator FST dump
-/// This is an internally used class - see VerilatedFstC for what to call from applications
+// Base class to create a Verilator FST dump
+// This is an internally used class - see VerilatedFstC for what to call from applications
 
 class VerilatedFst final : public VerilatedTrace<VerilatedFst> {
 private:
@@ -86,23 +85,23 @@ public:
     explicit VerilatedFst(void* fst = nullptr);
     ~VerilatedFst();
 
-    /// Open the file; call isOpen() to see if errors
+    // Open the file; call isOpen() to see if errors
     void open(const char* filename) VL_MT_UNSAFE;
-    /// Close the file
+    // Close the file
     void close() VL_MT_UNSAFE;
-    /// Flush any remaining data to this file
+    // Flush any remaining data to this file
     void flush() VL_MT_UNSAFE;
-    /// Is file open?
+    // Return if file is open
     bool isOpen() const { return m_fst != nullptr; }
 
     //=========================================================================
     // Internal interface to Verilator generated code
 
-    /// Inside dumping routines, declare a data type
+    // Inside dumping routines, declare a data type
     void declDTypeEnum(int dtypenum, const char* name, vluint32_t elements,
                        unsigned int minValbits, const char** itemNamesp, const char** itemValuesp);
 
-    /// Inside dumping routines, declare a signal
+    // Inside dumping routines, declare a signal
     void declBit(vluint32_t code, const char* name, int dtypenum, fstVarDir vardir,
                  fstVarType vartype, bool array, int arraynum);
     void declBus(vluint32_t code, const char* name, int dtypenum, fstVarDir vardir,
@@ -135,16 +134,18 @@ class VerilatedFstC final {
     VL_UNCOPYABLE(VerilatedFstC);
 
 public:
+    /// Construct the dump. Optional argument is ignored.
     explicit VerilatedFstC(void* filep = nullptr)
         : m_sptrace{filep} {}
+    /// Destruct, flush, and close the dump
     ~VerilatedFstC() { close(); }
     /// Routines can only be called from one thread; allow next call from different thread
     void changeThread() { spTrace()->changeThread(); }
 
-    // ACCESSORS
-    /// Is file open?
+    // METHODS - User called
+
+    /// Return if file is open
     bool isOpen() const { return m_sptrace.isOpen(); }
-    // METHODS
     /// Open a new FST file
     void open(const char* filename) VL_MT_UNSAFE_ONE { m_sptrace.open(filename); }
     /// Close dump
@@ -158,16 +159,22 @@ public:
     void dump(double timestamp) { dump(static_cast<vluint64_t>(timestamp)); }
     void dump(vluint32_t timestamp) { dump(static_cast<vluint64_t>(timestamp)); }
     void dump(int timestamp) { dump(static_cast<vluint64_t>(timestamp)); }
-    /// Set time units (s/ms, defaults to ns)
-    /// For Verilated models, these propage from the Verilated default --timeunit
+
+    // METHODS - Internal/backward compatible
+    // \protectedsection
+
+    // Set time units (s/ms, defaults to ns)
+    // Users should not need to call this, as for Verilated models, these
+    // propage from the Verilated default timeunit
     void set_time_unit(const char* unitp) { m_sptrace.set_time_unit(unitp); }
     void set_time_unit(const std::string& unit) { m_sptrace.set_time_unit(unit); }
-    /// Set time resolution (s/ms, defaults to ns)
-    /// For Verilated models, these propage from the Verilated default --timeunit
+    // Set time resolution (s/ms, defaults to ns)
+    // Users should not need to call this, as for Verilated models, these
+    // propage from the Verilated default timeprecision
     void set_time_resolution(const char* unitp) { m_sptrace.set_time_resolution(unitp); }
     void set_time_resolution(const std::string& unit) { m_sptrace.set_time_resolution(unit); }
 
-    /// Internal class access
+    // Internal class access
     inline VerilatedFst* spTrace() { return &m_sptrace; };
 };
 
diff --git a/include/verilated_trace.h b/include/verilated_trace.h
index dd98ce2b1..37664caf2 100644
--- a/include/verilated_trace.h
+++ b/include/verilated_trace.h
@@ -12,10 +12,9 @@
 //=============================================================================
 ///
 /// \file
-/// \brief Tracing functionality common to all formats
+/// \brief Internal tracing functionality common to all formats
 ///
 //=============================================================================
-// SPDIFF_OFF
 
 #ifndef VERILATOR_VERILATED_TRACE_H_
 #define VERILATOR_VERILATED_TRACE_H_
@@ -221,9 +220,9 @@ protected:
 
     void declCode(vluint32_t code, vluint32_t bits, bool tri);
 
-    /// Is this an escape?
+    // Is this an escape?
     bool isScopeEscape(char c) { return c != '\f' && (isspace(c) || c == m_scopeEscape); }
-    /// Character that splits scopes.  Note whitespace are ALWAYS escapes.
+    // Character that splits scopes.  Note whitespace are ALWAYS escapes.
     char scopeEscape() { return m_scopeEscape; }
 
     void close();
diff --git a/include/verilated_trace_imp.cpp b/include/verilated_trace_imp.cpp
index aa4a6c233..04caffa2b 100644
--- a/include/verilated_trace_imp.cpp
+++ b/include/verilated_trace_imp.cpp
@@ -15,7 +15,6 @@
 /// \brief Implementation of tracing functionality common to all trace formats
 ///
 //=============================================================================
-// SPDIFF_OFF
 
 // clang-format off
 
diff --git a/include/verilated_vcd_c.cpp b/include/verilated_vcd_c.cpp
index c379b678a..d0f1f6d8c 100644
--- a/include/verilated_vcd_c.cpp
+++ b/include/verilated_vcd_c.cpp
@@ -15,7 +15,6 @@
 /// \brief C++ Tracing in VCD Format
 ///
 //=============================================================================
-// SPDIFF_OFF
 
 // clang-format off
 
@@ -34,8 +33,6 @@
 # include <unistd.h>
 #endif
 
-// SPDIFF_ON
-
 #ifndef O_LARGEFILE  // For example on WIN32
 # define O_LARGEFILE 0
 #endif
diff --git a/include/verilated_vcd_c.h b/include/verilated_vcd_c.h
index a2503339a..ed02cbda1 100644
--- a/include/verilated_vcd_c.h
+++ b/include/verilated_vcd_c.h
@@ -15,7 +15,6 @@
 /// \brief C++ Tracing in VCD Format
 ///
 //=============================================================================
-// SPDIFF_OFF
 
 #ifndef VERILATOR_VERILATED_VCD_C_H_
 #define VERILATOR_VERILATED_VCD_C_H_
@@ -29,7 +28,6 @@
 
 class VerilatedVcd;
 
-// SPDIFF_ON
 //=============================================================================
 // VerilatedFile
 /// File handling routines, which can be overrode for e.g. socket I/O
@@ -48,8 +46,8 @@ public:
 
 //=============================================================================
 // VerilatedVcd
-/// Base class to create a Verilator VCD dump
-/// This is an internally used class - see VerilatedVcdC for what to call from applications
+// Base class to create a Verilator VCD dump
+// This is an internally used class - see VerilatedVcdC for what to call from applications
 
 class VerilatedVcd VL_NOT_FINAL : public VerilatedTrace<VerilatedVcd> {
 private:
@@ -136,19 +134,19 @@ public:
     ~VerilatedVcd();
 
     // ACCESSORS
-    /// Set size in megabytes after which new file should be created
+    // Set size in megabytes after which new file should be created
     void rolloverMB(vluint64_t rolloverMB) { m_rolloverMB = rolloverMB; }
 
     // METHODS
-    /// Open the file; call isOpen() to see if errors
+    // Open the file; call isOpen() to see if errors
     void open(const char* filename) VL_MT_UNSAFE_ONE;
-    /// Open next data-only file
+    // Open next data-only file
     void openNext(bool incFilename) VL_MT_UNSAFE_ONE;
-    /// Close the file
+    // Close the file
     void close() VL_MT_UNSAFE_ONE;
-    /// Flush any remaining data to this file
+    // Flush any remaining data to this file
     void flush() VL_MT_UNSAFE_ONE;
-    /// Is file open?
+    // Return if file is open
     bool isOpen() const { return m_isOpen; }
 
     //=========================================================================
@@ -211,8 +209,8 @@ public:
         chgDouble(oldp - this->oldp(0), newval);
     }
 
-    /// Inside dumping routines, dump one signal, faster when not inlined
-    /// due to code size reduction.
+    // Inside dumping routines, dump one signal, faster when not inlined
+    // due to code size reduction.
     void fullBit(vluint32_t code, const vluint32_t newval);
     void fullBus(vluint32_t code, const vluint32_t newval, int bits);
     void fullQuad(vluint32_t code, const vluint64_t newval, int bits);
@@ -225,8 +223,8 @@ public:
                       int bits);
     void fullDouble(vluint32_t code, const double newval);
 
-    /// Inside dumping routines, dump one signal if it has changed.
-    /// We do want to inline these to avoid calls when the value did not change.
+    // Inside dumping routines, dump one signal if it has changed.
+    // We do want to inline these to avoid calls when the value did not change.
     inline void chgBit(vluint32_t code, const vluint32_t newval) {
         vluint32_t diff = oldp(code)[0] ^ newval;
         if (VL_UNLIKELY(diff)) fullBit(code, newval);
@@ -336,17 +334,19 @@ class VerilatedVcdC VL_NOT_FINAL {
     VL_UNCOPYABLE(VerilatedVcdC);
 
 public:
+    /// Construct the dump. Optional argument is a preconstructed file.
     explicit VerilatedVcdC(VerilatedVcdFile* filep = nullptr)
         : m_sptrace{filep} {}
+    /// Destruct, flush, and close the dump
     ~VerilatedVcdC() { close(); }
     /// Routines can only be called from one thread; allow next call from different thread
     void changeThread() { spTrace()->changeThread(); }
 
 public:
-    // ACCESSORS
-    /// Is file open?
+    // METHODS - User called
+
+    /// Return if file is open
     bool isOpen() const { return m_sptrace.isOpen(); }
-    // METHODS
     /// Open a new VCD file
     /// This includes a complete header dump each time it is called,
     /// just as if this object was deleted and reconstructed.
@@ -368,16 +368,22 @@ public:
     void dump(double timestamp) { dump(static_cast<vluint64_t>(timestamp)); }
     void dump(vluint32_t timestamp) { dump(static_cast<vluint64_t>(timestamp)); }
     void dump(int timestamp) { dump(static_cast<vluint64_t>(timestamp)); }
-    /// Set time units (s/ms, defaults to ns)
-    /// For Verilated models, these propage from the Verilated default --timeunit
+
+    // METHODS - Internal/backward compatible
+    // \protectedsection
+
+    // Set time units (s/ms, defaults to ns)
+    // Users should not need to call this, as for Verilated models, these
+    // propage from the Verilated default timeunit
     void set_time_unit(const char* unit) { m_sptrace.set_time_unit(unit); }
     void set_time_unit(const std::string& unit) { m_sptrace.set_time_unit(unit); }
-    /// Set time resolution (s/ms, defaults to ns)
-    /// For Verilated models, these propage from the Verilated default --timeunit
+    // Set time resolution (s/ms, defaults to ns)
+    // Users should not need to call this, as for Verilated models, these
+    // propage from the Verilated default timeprecision
     void set_time_resolution(const char* unit) { m_sptrace.set_time_resolution(unit); }
     void set_time_resolution(const std::string& unit) { m_sptrace.set_time_resolution(unit); }
 
-    /// Internal class access
+    // Internal class access
     inline VerilatedVcd* spTrace() { return &m_sptrace; }
 
 #ifdef VL_TRACE_VCD_OLD_API
@@ -385,7 +391,8 @@ public:
     // Note: These are only for testing for backward compatibility with foreign
     // code and is not used by Verilator. Do not use these as there is no
     // guarantee of functionality.
-    /// Use evcd format
+
+    // Use evcd format
     void evcd(bool flag) VL_MT_UNSAFE_ONE { m_sptrace.evcd(flag); }
 #endif
 };
diff --git a/include/verilated_vcd_sc.cpp b/include/verilated_vcd_sc.cpp
index d5ccb0df4..215139022 100644
--- a/include/verilated_vcd_sc.cpp
+++ b/include/verilated_vcd_sc.cpp
@@ -15,12 +15,10 @@
 /// \brief Verilator tracing in VCD Format
 ///
 //=============================================================================
-// SPDIFF_OFF
 
 #include "verilatedos.h"
 #include "verilated_vcd_sc.h"
 
-// SPDIFF_ON
 //======================================================================
 //======================================================================
 
diff --git a/include/verilated_vcd_sc.h b/include/verilated_vcd_sc.h
index 3568d6d17..2c7fe4cc2 100644
--- a/include/verilated_vcd_sc.h
+++ b/include/verilated_vcd_sc.h
@@ -15,7 +15,6 @@
 /// This class is not threadsafe, as the SystemC kernel is not threadsafe.
 ///
 //=============================================================================
-// SPDIFF_OFF
 
 #ifndef VERILATOR_VERILATED_VCD_SC_H_
 #define VERILATOR_VERILATED_VCD_SC_H_
@@ -24,18 +23,18 @@
 #include "verilated_sc.h"
 #include "verilated_vcd_c.h"
 
-// SPDIFF_ON
 //=============================================================================
 // VerilatedVcdSc
 ///
-/// This class is passed to the SystemC simulation kernel, just like a
-/// documented SystemC trace format.
+/// This class creates a Verilator-friendly VCD trace format with the
+/// SystemC simulation kernel, just like a SystemC-documented trace format.
 
 class VerilatedVcdSc final : sc_trace_file, public VerilatedVcdC {
     // CONSTRUCTORS
     VL_UNCOPYABLE(VerilatedVcdSc);
 
 public:
+    /// Construct a SC trace object, and register with the SystemC kernel
     VerilatedVcdSc() {
         sc_get_curr_simcontext()->add_trace_file(this);
         // We want to avoid a depreciated warning, but still be back compatible.
@@ -48,16 +47,17 @@ public:
         }
         spTrace()->set_time_resolution(sc_get_time_resolution().to_string());
     }
+    /// Destruct, flush, and close the dump
     virtual ~VerilatedVcdSc() { close(); }
 
-    // METHODS
-    /// Called by SystemC simulate()
+    // METHODS - for SC kernel
+    // Called by SystemC simulate()
     virtual void cycle(bool delta_cycle) {
         if (!delta_cycle) this->dump(sc_time_stamp().to_double());
     }
 
 private:
-    /// Fake outs for linker
+    // METHODS - Fake outs for linker
 
 #ifdef NC_SYSTEMC
     // Cadence Incisive has these as abstract functions so we must create them
diff --git a/include/verilated_vpi.h b/include/verilated_vpi.h
index c7b5946aa..2e2d125a5 100644
--- a/include/verilated_vpi.h
+++ b/include/verilated_vpi.h
@@ -47,7 +47,8 @@ public:
     /// Returns time of the next registered VPI callback, or
     /// ~(0) if none are registered
     static QData cbNextDeadline() VL_MT_UNSAFE_ONE;
-    /// Self test, for internal use only
+
+    // Self test, for internal use only
     static void selfTest() VL_MT_UNSAFE_ONE;
 };