I agree with this. In the same way internet is synonymous with Facebook in some countries, I think any kind of niche community defaults to congregating in a subreddit. Sometimes I'd even describe HN as a subreddit focused on tech and entrepreneurship to describe it to people who don't know much about it.

Subreddits are almost different websites with different moderators and different cultures. HN is now one of the only forums I consistently visit. Otherwise subreddits dominate this method of topic-focused discussion.

Lots of censorship going on however. There are sites that show the deleted comments and you can learn a lot about the agenda of reddit from those. It's interesting in its own right.

On reddit, when comments say [deleted] its because the user deleted it themselves. But, yeah, there is censorship on reddit. It's almost always by subreddit mods and not reddit admins.