(OK one last comment on this, it’s kind of minor, but for some valid code is essential)

Well, the list is not very long – there is already a comprehensive list of tags in WP, in wp-includes/kes.php. So the issue is removing stuff from it rather than the other way around.

I went through the list in full (earlier I had only checked tags allowed in comments) and there are only five tags altogether. For completeness sake, here they are, in my dirty quick ‘fix’ to disallow them
unset( $allowedposttags['acronym'] );
unset( $allowedposttags['strike'] );
unset( $allowedposttags['big'] );
unset( $allowedposttags['font'] );
unset( $allowedposttags['tt'] );

unset( $allowedtags['acronym'] );
unset( $allowedtags['strike'] );


If I ever get around doing it ‘properly’, i.e. mapping them to valid tags instead of removing them, I will post another comment.

Thanks again for your great work.