What's the expected damage? A bad post?
Moderately bad posts that appear to be warmly supported by the community. This sends incorrect signals about the community to members of the community.
I see what you're saying here, but this strikes me as difficult to sustain, and liable to working too hard to defend purity at the cost of the valuable good faith outside view. YMMV, of course.
I just noticed that calcsam, who just posted two top posts in the main section of the site, only has the 100 karma that he has, so far, gained from those posts.
I don't object to those posts being there, but how did he do that?
Edit: Question answered; Eliezer mucked around with the karma system to make this possible in this specific case.