Unless you've got something newer to suggest otherwise, that's how HN operates. "Downvotes aren't for disagreeing" is an absurd redditism (everyone knows that they are, since upvotes are for agreeing).

It's a little different on HN due to how the comments are hidden quite quickly when downvoted. I frequently upvote people who reply to me but I disagree with, simply because it would ruin the comment chain and hey, they might just be right anyway ;)

I reserve downvotes for rudeness and demonstrably wrong/misleading comments.

I can understand a downvote with a solid reply, but downvote just for disagreeing doesn't add to the discussion, its more of a censorship which should only be used for offensive/misleading comments IMHO.

Personally, I use upvotes to reward new knowledge or an interesting argument in a comment, I don't upvote every comment I agree with, and downvote only if the comment is offensive.

So then the end result is that opinions/comments that a lot of people disagree with will get punished? Seems counter-intuitive if you're trying to have a reasonable argument/discussion/debate about something. It's one thing to express disagreement, but it's completely different to silence + punish someone because you disagree with them.