The criteria for comments on HN is actually fairly demanding [https://news.ycombinator.com/newswelcome.html]. If your comment does not teach something, if it's not positive or civil, or if it's rude or dumb, it's basically supposed to be downvoted automatically.
The kinds of comments that get downvoted the most are negative ones (obviously), followed by generalized opinions, attempts at jokes, politics, and finally, meta-complaints about the discourse on HN. In doing so, it raises the value of the site for people who don't find those kind of comments deeply interesting.
On a personal level, it gets really, really old when people complain about how unfairly other people treat them. If you're getting downvoted and you don't want to be downvoted, either change your tune to get upvotes, move on to a community that likes you the way you are, or stop caring if you're downvoted or not.