I think I never downvoted anyone on hackernews yet - it just does not seem important.

On reddit on the other hand, I just had to downvote wrong opinions. This works to some extent, until moderators interfere and ban you. That part made me stop use reddit actually, in particular since someone made a complaint and I got banned for some days. I objected and the moderators of course did not respond. I can not allow random moderators to just chime in arbitrarily and flag "this comment you made is a threat", when it clearly was not. But you can not really argue with reddit moderators.