Ask about HN: Caching in place?

I've noticed that the site has been behaving erratically lately. After posting a comment, sometimes I see the comment I replied to with the "reply box" instead of my comment. Sometimes when I click "threads", I see very out-of-date information. Sometimes I see the version of the page for a non-logged-in-user. This happens with the front page, too.

All this suggests that there is some sort of bug in the caching mechanism, or something. Just thought I would bring this to pg's attention (and am wondering why the caching is now necessary, too).