HN is heavily moderated, and it has a nerdy subject matter that selects for a certain type of audience. Those both help, but I think the biggest thing that makes HN so great is its peculiar business model.
I don't know if YC keep this site running purely out of love or if it's a calculated ploy to make money, but if HN is profitable for YC then it's in a very indirect and hard-to-quantify way - e.g. YC startups using HN as a recruitment platform. Dang doesn't have money-hungry VCs breathing down his neck telling him to maximize "engagement" - the day that happens will be the day HN devolves into an unreadable, unusable pile of garbage, like what happened to Reddit.
There aren't many communities like HN because there aren't many organizations that have the resources to run a site like this without running it into the ground because they have dollar signs in their eyes. The few that do exist are probably small forums focused on a super-niche topic or hobby, but if I knew of them I wouldn't post them here because I wouldn't want to spoil the secret.
I don't know if YC keep this site running purely out of love or if it's a calculated ploy to make money, but if HN is profitable for YC then it's in a very indirect and hard-to-quantify way - e.g. YC startups using HN as a recruitment platform. Dang doesn't have money-hungry VCs breathing down his neck telling him to maximize "engagement" - the day that happens will be the day HN devolves into an unreadable, unusable pile of garbage, like what happened to Reddit.
There aren't many communities like HN because there aren't many organizations that have the resources to run a site like this without running it into the ground because they have dollar signs in their eyes. The few that do exist are probably small forums focused on a super-niche topic or hobby, but if I knew of them I wouldn't post them here because I wouldn't want to spoil the secret.