This forum is pretty heavily moderated, and its usefulness is largely because it is moderated. Back in the early days of HN the comparison was Reddit, which at

This forum is pretty heavily moderated, and its usefulness is largely because it is moderated. Back in the early days of HN the comparison was Reddit, which at the time was completely unmoderated (they didn't have subreddits or mods at the time), and Reddit was starting to become a cesspool of spam, low-effort posts, and offensive content. Many people moved over to HN simply because it avoided that. (And Reddit ended up introducing moderation a couple years later.) Unmoderated forums work fine when they're a small group of people with a vested interest in preserving the norms of the community. They fail quickly if they can't establish barriers against the outside world that prevent people with no skin in the game from hijacking the community for their own agendas. The modern Internet is much more similar to the latter than the former.