diff --git a/mps/code/arenacl.c b/mps/code/arenacl.c
index 0ff7a21d3f2..e8be0b3390c 100644
--- a/mps/code/arenacl.c
+++ b/mps/code/arenacl.c
@@ -100,7 +100,7 @@ static Res clientChunkCreate(Chunk *chunkReturn, Addr base, Addr limit,
 
   AVER(chunkReturn != NULL);
   AVER(base != (Addr)0);
-  /* @@@@ Should refuse on small chunks, instead of AVERring. */
+  /* TODO: Should refuse on small chunks, instead of AVERring. */
   AVER(limit != (Addr)0);
   AVER(limit > base);
 
@@ -113,7 +113,7 @@ static Res clientChunkCreate(Chunk *chunkReturn, Addr base, Addr limit,
     goto failBootInit;
 
   /* Allocate the chunk. */
-  /* See <design/arena/>.@@@@ */
+  /* TODO: Add reference to design. */
   res = BootAlloc(&p, boot, sizeof(ClientChunkStruct), MPS_PF_ALIGN);
   if (res != ResOK)
     goto failChunkAlloc;
@@ -152,7 +152,9 @@ static Res ClientChunkInit(Chunk chunk, BootBlock boot)
   AVERT(BootBlock, boot);
   UNUSED(boot);
 
-  clChunk->freePages = chunk->pages; /* too large @@@@ */
+  /* TODO: An old comment claimed this is too large.
+     Does it fail to exclude the page table or something? */
+  clChunk->freePages = chunk->pages;
 
   return ResOK;
 }
diff --git a/mps/code/arenavm.c b/mps/code/arenavm.c
index 8061765cc6c..c71288172dc 100644
--- a/mps/code/arenavm.c
+++ b/mps/code/arenavm.c
@@ -30,8 +30,10 @@
 SRCID(arenavm, "$Id$");
 
 
-/* @@@@ Arbitrary calculation for the maximum number of distinct */
-/* object sets for generations.  Should be in config.h. */
+/* Arbitrary calculation for the maximum number of distinct */
+/* object sets for generations. */
+/* TODO: Should be in config.h. */
+/* TODO: The arena shouldn't be managing generations */
 /* .gencount.const: Must be a constant suitable for use as an */
 /* array size. */
 #define VMArenaGenCount ((Count)(MPS_WORD_WIDTH/2))
@@ -391,7 +393,7 @@ static Res VMChunkInit(Chunk chunk, BootBlock boot)
     goto failnoSparePages;
   vmChunk->noSparePages = p;
 
-  /* Actually commit all the tables. <design/arenavm/>.@@@@ */
+  /* Map memory for the bit tables. */
   overheadLimit = AddrAdd(chunk->base, (Size)BootAllocated(boot));
   if (vmChunk->overheadMappedLimit < overheadLimit) {
     overheadLimit = AddrAlignUp(overheadLimit, ChunkPageSize(chunk));
@@ -1079,7 +1081,7 @@ static Bool pagesFindFreeWithSegPref(Index *baseReturn, VMChunk *chunkReturn,
     preferred = pref->zones;
   }
 
-  /* @@@@ Some of these tests might be duplicates.  If we're about */
+  /* Some of these tests might be duplicates.  If we're about */
   /* to run out of virtual address space, then slow allocation is */
   /* probably the least of our worries. */
 
diff --git a/mps/code/buffer.c b/mps/code/buffer.c
index e7946dda64f..c63310980ee 100644
--- a/mps/code/buffer.c
+++ b/mps/code/buffer.c
@@ -778,7 +778,8 @@ Bool BufferCommit(Buffer buffer, Addr p, Size size)
   /* .commit.after: If a flip occurs at this point, the pool will */
   /* see "initAtFlip" above the object, which is valid, so it will */
   /* be collected.  The commit must succeed when trip is called.  */
-  /* The pointer "p" will have been fixed up.  (@@@@ Will it?) */
+  /* The pointer "p" will have been fixed up. */
+  /* TODO: Check the above assertion and explain why it is so. */
   /* .commit.trip: Trip the buffer if a flip has occurred. */
   if (buffer->ap_s.limit == 0)
     return BufferTrip(buffer, p, size);
@@ -887,7 +888,7 @@ void BufferFlip(Buffer buffer)
       && !BufferIsReset(buffer)) {
     AVER(buffer->initAtFlip == (Addr)0);
     buffer->initAtFlip = buffer->ap_s.init;
-    /* Memory Barrier here? @@@@ */
+    /* TODO: Is a memory barrier required here? */
     buffer->ap_s.limit = (Addr)0;
     buffer->mode |= BufferModeFLIPPED;
   }