I think OP is pointing out the irony that HN is popular among people who claim to not accept that.

People try to make the argument that Twitter and (maybe to a lesser extent) Facebook are akin to a "town square", whereas I don't think people consider the HN comments section a "town square".

HN as a platform is effectively dedicated to a narrow set of topics, with a largely homogeneous user base (compared to any mainstream social media at least). I don’t think the consensus here is particularly favourable towards free speech, and it certainly has a very narrow Overton Window of acceptable ideas. The user moderation features also heavily reinforce whatever groupthink is popular, you have to “accepted” by accumulating a large amount of karma to influence voting, and 4 in-group users disagreeing with a comment is enough to remove it from the discussion.

I think Dang’s moderation is usually pretty decent, but I really don’t think this is a place where free speech is championed. In any thread on the topic, calls for increased speech regulation seem to be very popular.

I've been lurking on HN for about the last 8 years or so but only a few years ago made an account and I sparsely comment. Only a couple of weeks ago was my account considered worthy of being able to vote down. Meanwhile I've seen users essentially "game" their comment karma to high amounts within a few weeks.

I don't really agree with the idea that this place is an echo chamber, but I do sort of see it as similar to an IT meetup. You generally don't go to an IT focused meetup and start talking about abortion, religion, etc. and nobody would be surprised if you were kindly asked to leave the venue if you insisted on soap-boxing. If someone came and carted you off in a black van for speaking in a public place about your feelings on abortion I'd expect there to be a lot of push back from the public.

Politics is discussed all the time in HN. It’s not a generally taboo topic at all.

I don’t think I’d go as far as saying it’s a full blown echo chamber either. But theres a pretty clear orthodoxy on certain topics here.

I think it's discussed only where it's considered "on-topic". In my experience, many politcal articles are quickly removed as off-topic unless there's some technological bend to it. For example, politics in a thread about Julia 1.7 release would be "off-topic", politics in a thread about net neutrality might be on-topic but only up to a certain degree.