I'm not sure who to file the bug against: sizzle or webkit. I'll file another bug against sizzle. if anything, expected behavior for webkit could be to still throw an exception if the :first pseudo-selector is found outside of an @page rule context.
jquery bug filed here: http://dev.jquery.com/ticket/6519
thinking I should post in radar to get more attention. ;)
*** This bug has been marked as a duplicate of bug 38697 ***
Thanks for following up on this.
>thinking I should post in radar to get more attention. ;)
Sorry for having overlooked your earlier report. It's usually helpful to structure high importance bug reports like this around a specific user observable symptom (like "www.example.org no longer works in r12345 nightly"), as this gets more eyes looking at the issue.