Well, it finally happened–SpamKarma2 finally let a piece of spam slip into my comments. I installed SK2 about 4.5 months ago, and it’s caught 268 spams out of 269 attempts (99.63% accuracy). It hasn’t yet mischaracterized a “real” comment as spam.
The comment which finally got through had a very short, grammatically correct phrase. It had a valid javascript payload, and the encrypted payload was valid. The spam had an author URL which pointed to a domain that was for sale.