Interestingly, the heat for this pattern is always taken by the last comment, for some strange reason. Maybe it's the communities way of saying "Duh, we know this happens, and the way we stop conversations from going down the meta-toilet is to not have them." Although I would say it's more fair to downvote every comment that fits the pattern, to the root, rather than just the latter ones.

>Although I would say it's more fair to downvote every comment that fits the pattern, to the root, rather than just the latter ones.

That's a good way to lose your comment-voting privileges - I just noticed my ability to vote on comments disappeared at some point.