Zalgo-ized comments cause Safari to crash.
If I go to RegEx match open tags except XHTML self-contained tags, and the Zalgo-ized comment isn't visible, I can do command and F fine.
However, if I click on "show 46 more comments" underneath bobince's answer, and then do command and F, the browser crashes.
Likewise, if I go to Is it true that if someone reaches 200k reputation he/she gets a painting with a unicorn on it?, where a Zalgo-ized comment is already visible, and do command and F, the browser crashes.
I'm on Safari Version 6.1.5 (7537.77.4), on Mac OS X Lion 10.7.5 (11G63).