Editting bugs
This has been present since about forever, but I keep forgetting to mention it:
1) When you edit a post within the 10 minute window, if you attempt to change the post to anonymous coward, or an anon post to a normal post, it's accepted, but not acted upon.
2) If you edit a post, and the ediited post contains invalid html, when you submit, whilst the page does return to the editting screen, the big warning "Your post contains invalid HTML" isn't displayed, and on more than one occasion I've clicked away without noticing the problem.
Cheers!