It appears exactly as described on Safari, Firefox and Opera on my Mac and only in threaded view, so it's most likely not a browser issue. And I only have an adblocker on FF, so shouldn't be that either.

OTOH, I've only managed to reproduce the issue with the mentioned thread, others show just fine in the threaded view. Might have something to do with the reply depth, actually and the title not fitting properly in its field anymore:

I'd also look into making the HTML output as valid as possible, as invalid HTML can cause all sorts of funkiness. 55 to 59 validation errors is actually pretty bad. Then again, most probably go away by fixing some syntax error at the beginning part of the template.
Yes. I can haz a biz and site, no?