I'm back to work and going hard at it. Lots to do.
The spam problem is getting unmanageable again, even with MT-Blacklist. I'm trying to nag my admin into upgrading our Movable Type installation because the new version supposedly has a new system that resolves a lot of the spam issues. Until then, my motivation is low because it takes hours to delete the spam.
Can't you just have a captcha required for writing comments? I'm sure it would make things easier on your end. As for me (and your other readers), the slight annoyance of having to complete a captcha every time I write a comment would, in my opinion, be smaller over time than the occasional but significant annoyance of writing a long comment and then have it be rejected as spam... Maybe that happens more with me than with other people, though.