> HN tends to downvote any political comments, especially comments that turn the discussion more political, even in a story that already tangentially touches on politics
That's... really not true. Case-in-point: look at any frontpage post that talks about health insurance, wage floors, guaranteed minimum income, etc. There's a clearly dominant opinion, and left-leaning opinions tend to be the most frequently-posted (as well as the most frequently upvoted). This is ignoring tech-politics (ie, net neutrality, digital privacy).
People do use the downvote as a signal of disagreement (which is a problem[0], because it just polarizes discussions even more by driving away constructive, dissenting opinions[1]). But the people who downvote any political sentiment don't outweigh the rest, as evidenced by the end results.
[0] To pre-empt the perennial debate on whether downvoting purely for disagreement is bad, here are dang's thoughts on the matter: https://news.ycombinator.com/item?id=7606517
[1] There are topics on which I have a lot of domain knowledge relative to the typical HN commenter. I used to be more proactive with sharing this information in HN comments when relevant, but I only do this a small fraction of the time compared to a few years ago[2]. There's nothing more discouraging than writing a 500-word comment with multiple footnotes and external citations to primary sources and peer-reviewed articles, only to be downvoted for expressing a contrary opinion, or even simply a more nuanced version of the dominant one.
[2] I won't say whether it's gotten better or worse, but I've certainly learned from those experiences over time, and from my observations, so have other users.