>Too many people come here from reddit with the mentality that downvote is for disagreement.
I'm not so sure about that.
I came from Reddit too, however I've been here for months now, and I still can't downvote anyone. From what I'm told, you need a karma of 1000 to get that ability. I can only upvote.
So, you have to be a longtime HNer to even have this ability to silence other peoples' opinions. You cannot be some newbie here and downvote people, unless you hit the karma jackpot by making a few posts that get hundreds and hundreds of upvotes.
Therefore, I think it's much more likely that what you're seeing (dissenting opinions being downvoted) is coming from both the heavy-handed non-transparent moderators, and from others in their "inner circle" of longtime members.