Reverse thread sorting by most recent number

[Christoph Groth]

Hello,

I have set gnus-thread-sort-functions to
'(gnus-thread-sort-by-most-recent-number) and this works as it should.

Now I would like to reverse the sorting order so that the order of
threads is consistent with the chronological order of messages within a
thread.

I defined a function

(defun my-thread-sort-by-most-recent-number-reversed (h1 h2)
  "Sort threads such that the thread with the most recently arrived article 
comes last."
  (< (gnus-thread-highest-number h1) (gnus-thread-highest-number h2)))

that should return the negation of
gnus-thread-sort-by-most-recent-number, but setting
gnus-thread-sort-functions to it does not seem to work.  Single messages
are sorted as expected, and new messages tend to appear at the back of
the buffer, but in some cases threads with new messages are stuck above
older ones.  The sorting order of threads is clearly not the opposite of
the one given by gnus-thread-sort-by-most-recent-number.

I have no clue why Gnus behaves like this...  Anyone has an idea?

Cheers
Christoph