Imagine we had never heard of this "comments" idea. How would we design such a feature? For starters, we'd need moderation. Some automated spam blocking. Voting might be a nice feature to draw attention to good comments. Reputation for the participants might help.

We'd end up reinventing HN, Reddit, Digg, &c. One of the reasons I prefer to link to HN is that there is a community with a well-understood standard for behaviour. If I had my own comments, I'd have to ask people to live up to some set of arbitrary standards, and that's a lot to ask when someone might only read one thing from me every month or so.

This is just the first time I've seen it. I wonder what the policy is on creating an off-site mechanism to post to Hacker News. I looked over the various APIs and none seem to offer a method to post a link. They're mainly read-only.