Great idea, I think cross checking all comments would be too much, but I could start doing that if the commenters' score reached say -20. then as you say see how many of their past, say, 100 comments, repeat. If too many do, blacklist.

A problem with warning them is, my own bot will get flagged by itself, lol. This means that there are other bots out there that will get caught up. Maybe I could just have an exemption list. But would probably need to manually do that