It's very annoying that 100+ karma users could act as really good trolls, they could just go around and downvote everybody without ever loosing karma, but costing the commenter karma.
Don't get me wrong I really enjoy the HN community, there are a lot of bright people here and very good content and discussions, it's just that the system discourages you to have your own opinion on anything, because if you write something that a 100+ user doesn't like he can simply downvote you irresponsibly.
TL, DR: I don't know maybe it's me, maybe I have too radical opinions on stuff. But overall I feel that the downvoters should loose some karma too, and maybe force the downvoter to write a reason for it, to make sure that they downvote responsibly.
PS: I am not saying neither that I'm always right nor that I never deserved the downvote.