diff --git a/grp/simplerew.grp b/grp/simplerew.grp
index 9e5e918d52..d76c1949a3 100644
--- a/grp/simplerew.grp
+++ b/grp/simplerew.grp
@@ -10,6 +10,14 @@
 ##
 ##  Pre-computed confluent rewriting systems for certain simple groups,
 ##  that are not too large, but for which the calculation is slow.
+
+##  They have been created by the function `SplitBNRewritingPresentation`,
+##  typically with `weyl` and `borel` hand-selected and not computed by the
+##  generic routine. This data could be verified by calling
+##  `IsomorphismFpGroupForRewriting` on the respective simple group (which
+##  will fetch the data from this file) and verifying that the associated
+##  monoid presentation matches the generators, and is confluent.
+
 ##  They will be interpreted by the function `BuildRewritingFromData`.
 ##  The creator function `ConfluentRewritingData` is in a comment
 ##  in `lib.grpfpiso.gi`.
diff --git a/lib/gpfpiso.gi b/lib/gpfpiso.gi
index d9a843049b..fc59c9637b 100644
--- a/lib/gpfpiso.gi
+++ b/lib/gpfpiso.gi
@@ -1960,7 +1960,8 @@ local isob,isos,iso,gens,a,rels,l,i,j,bgens,cb,cs,b,f,k,w,monoid,
   dcnums:=List(dcnums,x->Immutable(Set(x)));
 
 
-  # ensure that weyl is rep, if new
+  # ensure that "weyl group" represents double cosets (but allow double
+  # coverage)
 
   rti:=List(dcnums,x->false); # which double are hit already
   for i in weyl do