The following lines in Render.pm

     # For most common alphabetic-only character encodings (i.e. iso-8859-*),
    # remove non-alpha characters 
    if( !defined($TWiki::cfg{Site}{CharSet}) ||
          $TWiki::cfg{Site}{CharSet} =~ /^iso-?8859-?/i ) {
        $anchorName =~ s/[^$TWiki::regex{mixedAlphaNum}]+/_/g;
    }

ensure that the FormattingTests? in the UnitTestContrib fail if you use a non-iso-8859-1 charset.

This impacts other tests as well, which can give misleading failures that take ages to track down.

TWikiFnTestCase? should be modified to enforce a setting for the site charset (and turn off locales). These features should be the subject of other tests.

-- TWiki:Main/CrawfordCurrie - 14 Jul 2008