It appears Movable Type has been 'eating' comments, taking actual non-spam comments and kicking them into the Spam Comments folder. It wasn't until a new reader asked about why several of her comments were never approved and/or never appeared that I looked into why they'd all up and disappeared. (All fixed now, Paulina! At least I think so....)
So I spent a couple of hours going through the Comments and Spam folders, setting things to rights...at least for comments posted over the last week or so. I only have another 1360 comments to go through.
I've never been able to leave comments (or at least have them show up), no didn't think anything about it. Sorry, maybe I should have spoken up a long time ago.