This is a followup on http://bugzilla.wikimedia.org/show_bug.cgi?id=5689
Indeed selecting revisions the history page so as to have them diff'ed works fine.
Yet the "← Previous diff" / "Next diff →" links on the diff pages themselves do weird things - at least hopping
back and forth with them does something different from selecting revisions on the history page one by one, which is
not very intuitive.