We had a major problem with spam (350K comments) and after the server went down under the weight of it all this weekend, we decided to get serious with the cleanup. We knocked out 250K by targeted SQL queries, and then went looking for a cleaner solution.
While wandering around the forums I saw http://forums.b2evolution.net/viewtopic.php?t=7577 EdB's experiment with deleting the entire anti-spam table. I tried it on our dev server - not deleting and leaving gone, but simply deleting and re-importing, to try to force a re-check of all the banned domains. They all imported correctly, but nothing was deleted. However, I then manually re-checked the word 'zoloft' and it found a comment to delete.
There's a whole list of expectations I had when I deleted our anti-spam entries, but that didn't meet any of them. Is this a bug? I would expect a full re-import would lead to a full re-check of our comments and trackbacks. Is this not the case?