I’ve grown tired of the problems with junk comments, false positives, and all the hassle involved in with handling this. My apologies if any of your comments failed to show up — MT reports they’ve been held for approval even if they have been identified as junk.
Essentially, I believe there are only two options that actually work: disable comments altogether, or use some CAPTCHA™ method. I’ve decided to do the latter, so comments now require a preview first, and then a 4-digit code. I’ve used the SCode plugin for Movable Type — all of the other Spam protection mechanisms built into MT never worked out for me (which makes me wonder why I don’t do what all the cool kids do and write my own blog software).
If you want to do me a favor, leave a comment and let me know if you run into any problems — via email if necessary.