They do not. Reddit has that rule, HN doesn't. (and old statements from moderators saying it's ok)

Can you point to that statement cause that seems contrary to establishing a civilized debate?

You downvote if something as an example is of topic or inflamatory or otherwise destroyes the conversation, not something you disagree with which is part of the discussion.

Never heard it was ok to downvote just because you disagree but would love to see the statement about that.

I can't point you to a specific place, but I recall that I made the same claim (downvote for disagree is wrong on HN), and deng corrected me.

I still think it's a lousy way to run a discussion. (Too low a bandwidth - you only get one bit of information.) But it seems to be the rules here.

/u/DanBC collected a few links a while back, I'll just link to his comment (HN search is broken for me right now): https://news.ycombinator.com/item?id=16440683

Thanks. I stand corrected I guess. Still, don't think it's a good way to show disagreement but fair enough.

It's certainly something the community is split about, but I'm not sure it could be fixed even if it were forbidden, seems almost impossible to police.