MT-Bayesian won't work (I know James has pretty much suggested people don't use, but not because it doesn't work), and Blacklist isn't enough. So I searched Feedster for some othe people having MT-Bayesian issues, and found some people using Scode to block at least the automated spambots.

Took some tweaking to get it to work, but you will now have to enter a security code to post a comment. The code will appear above the submit button as an image.