The comments I see getting crushed are really out there, but then I stay out of the political threads. I see downvotes as a way to sense the limits of the community without actually hurting anything.
If you lose enough karma over enough posts that you are losing privileges, it’s safe to assume that the damage you were doing to the discourse on this site was not completely harmless.
I learned that lesson by making a (what I thought was fairly respectful) joke about Mark Zuckerberg. I get my share of upvotes and downvotes, but that was the fastest I've ever seen it hit the floor. I'm not really a fan of the whole karma thing, but I think my biggest complaint is that when you post, it starts as 1, but doesn't change your overall score, so it's really 0, which would make more sense to me.