I'm easy either way --- I appreciate that it is a non-issue with new
formatting, but until developers can rely on the presence of Py >= 2.6,
%-formatting wil continue to be widely used.

Since optparse's special use of %-delimited tokens clashes with the
established formatting in a way that could arguably do with
clarification (I was blind enough to the solution to start this ticket),
I think it could be useful to document it close to the description of
%prog usage. Of course, since I now know the answer, *I* don't need it
to be in the documentation, but it might be helpful to others ;)