In my opinion,just like SO, downvotes should actually cost Karma. Yes sometimes some messages are just bad and trolling but sometimes people get downvoted just because they dont "go with the flow",and they have unpopular ideas. So if a downvote cost 2 , the downvoter should lose 1 for instance. And please dont downvote me just because you disagree.
EDIT: just proved my point,why am I being downvoted? it was a simple suggestion yet,someone downvoted me,just because he can and it's free. I was not trolling or anything... I just wanted to participate the debate.
I don't think I agree with this. Remember that downvotes on SO only have a cost when they're cast on answers, not questions, and that cost is a fraction of the gain from an upvote (1/2 for suggested edits to 1/10 answers).
It makes sense for downvotes to be free on questions and expensive on answers because questions are low effort while answers are high effort, and the community wants to encourage more answers.
On HN, everything is low effort, and everything is worth 1 point. Also, our problem with comments isn't that we don't have enough, it's that we have too many low effort/factually incorrect/abusive/spammy comments that we need to discourage. So it makes sense to keep downvotes free.
EDIT: just proved my point,why am I being downvoted? it was a simple suggestion yet,someone downvoted me,just because he can and it's free. I was not trolling or anything... I just wanted to participate the debate.