Delete trailing whitespace bug?

[Jose Antonio Ortega]

Hi. Since time immemorial, i've use delete-trailing-whitespace in my
write-file-hooks to ensure, well, that my files are saved without
trailing whitespaces. It works like a charm except for the fact that a
trailing vertical bar (|) is, apparently, considered whitespace; that
is, it's deleted when saving the file. This happened with emacs 21,
and happends too with emacs 22, both in GNU/Linux and Mac OS X.

Has anyone else observed this behaviour? Any ideas on what could be
causing it?

Thanks,
jao