[-] collapses the parent, you're correct. You can also unvote if you change your mind on your vote.
When logged in, I have upvote buttons on all comments, and I believe downvote buttons are enabled at over a certain amount of karma.
Even a comment like "fuck you you are dumb bastard hateful shit" tells me much more than a downvote. With comment like that I know that the opponent is not interested in productive conversation, so I move on.
And if people downvotes because they are emotional, this is not the place where I'd like to participate in discussions. I'm interested in the grown up respectful dispute and the extending each other world view.
A place where everyone agrees with each other is boring and a waste of time.
If everyone agreed there would be no need for voting, or even for comments. Very rarely do people gang up and down vote someone to oblivion, usually controversial opinions are up and down throughout the day. Plus there is a max amount of karma you can lose from down voting anyway, I think it's 5. It basically only affects new users who are out of line, or are trying to be provocative. I think it's the main thing that keeps HN the best forum on the internet. Well, third best thing behind dang, and sctb.
edit: also, HN is generally geared towards less comments of a higher quality. The biggest example is that if comments exceed votes by a certain amount, the story is automatically dropped from the front page.
Someone can disagree with you without you being wrong. If you think they are wrong in their response...what good is being done? If you both have intractable positions then more discussion on the topic is just lengthening scroll bars.
Additionally if I disagree with you or just think you're wrong I don't owe you any explanation of that. You don't have a right to my time because we disagree. It's not my job to convince you. I may choose to reply to you (as I obviously just have) but it's my choice entirely. You may reply back to me and I may never ever read it, I don't have any requirement to do so.
Just to be clear, you expect to get downvotes when mentioning LTSB? This does not match my experience, and I also made several LTSB mentions.
Just look at the recent threads where a submission was flagged and you will see a ton of them.
Unfortunately, HN isn't showing the data behind quantities but due to the oscillations we see, there are definitely significant amounts of downvoting occuring.