I think the danger with political discussion is that the expression of an idea is as important as the idea itself. This means that to have a productive political discussion you either need:

1. Very very high verbal skills so that each person can communicate their idea in a way that doesn't leave (much) room for interpretation or a bad-faith reading.

2. A community that "steelmans" each-other's ideas and consistently chooses the best-faith interpretation of what the other person is saying.

(1) is impossible in a forum that accepts folks from a range of backgrounds and abilities. (2) is generally impossible in a public forum on the internet. Even if everyone on Hacker News stuck to this principle, outsiders would not. You'd get posts on reddit about how "Hacker News is a haven for Nazis". Or posts on X about how "Communists are invading the tech community" and ultimately a lot of bad press for Y Combinator that I'm sure they'd rather not have.

Great points, I absolutely agree.