We're having some major performance problems, as is obvious from all the errors you're getting when you try to post comments. We had some substantial tweaks made to the code behind the scenes that was supposed to improve performance, but actually had exactly the opposite effect — now Scienceblogs is supposed to be bringing in some expert consultants very soon now to fix the problems, either rolling back the code or figuring out why we aren't getting any speed boost at all. I don't know when this will happen, since there are a lot of blogs here, and they all need to be patched somehow. We're all feeling a bit frustrated by the mess.
Almost always, though, when you post a comment, it is getting added to the database, even if it does bounce back with a timeout error or some other noise. Please don't just go back and repost the same comment again and again. Go back, reload the page, and see if your comment has appeared first.