Also, don't let downvotes discourage you. It's an experience to get a downvote on HN. Just try figure out why, a lot of the time it's unwarranted, a lot of the time it isn't. Learn from it as Mz says ;)
Honestly, I think that's the minority case here. I've rarely seen comments go to 0 or lower unless they were "objectively" bad, e.g. weren't interesting, were insulting, etc.
you forgot to mention smart ass remarks or lame attempts at humor. That's an easy way to get down voted. I've seen down votes also for opinions which go against the grain but those are rare, if you down vote something like that, at least post a reply.
Be polite, reread your post (I don't always do it) and bring something new.
I have temporarily, though you're right that it's uncommon for it to persist. I've quite often posted an opinion that was against the dominant opinion being expressed in a thread (with the person I was disagreeing with voted up to +10 or whatever), and got instantly voted down to a 0 or -1 score. But usually people will notice and upvote those back up again, at least into positive territory.
Of course some of those early downvotes might have been the notorious slipped-finger-downvoting instead (esp. on mobile devices), so hard to tell if it was really due to disagreement.
And keep in mind that some downvotes are just a slip of the finger. I occasionally ask for feedback if I find it too baffling. I don't bother if I knew the odds were good that my sense of humor was leading me astray but I just had to say it anyway. :-P
