HTML Brain Teaser

[zetetic]

I recently enabled HTML in posts on my forum, but only for members of the "Can use HTML" group. (Thanks to this handy hack.)

And one of my users immediately found a little bug. By putting:

<!--

in a post, he was able to screw up the postbit so bad the reply buttons were all gone and such. To prevent it, I tried all these tags after $post[message] in the postbit template:

<!-- comment -->
<!-- -->
<!---->
-->

But the first three had no effect (they just got commented out with everything else from the opening comment tag in the post) and the last one just showed up at the end of every post.

Can you think of a solution to this? (Besides disabling HTML )