I'm just putting this here in case it helps someone fix the problem, mods; feel free to delete this once things are fixed.

It seems posts with comments crash (so the bug's probably in the comment rendering code or something). Posts without comments can be read, so can the comment rss; inbox works but "view comments by user" doesn't ("view submitted" does).

(Don't reply to this, it'll make the page inaccessible :P)

So it's still possible to view existing posts (even with comments) through the rss feed, but not comment on them.

(My best bet would be something to do with comment karma calculation)

(Actually, after poking though recent commits on github, my bet would now be on comment retraction and deletion)