Comment #5 on issue 2838 by [email protected]: Patch: Changes less<Grob *> to Grob::less.
http://code.google.com/p/lilypond/issues/detail?id=2838
There might have been an oversight or confusion about what the followup code thinks about the resulting order, and in this case another sorting pass on whatever other criterion the followup code needs is required.
That is the problem - will change in new patch set.
