I think there’s a big difference between a site whose visible product is discussion, such as Hacker News, and a site whose discussion is only in support of the visible product, like Wikipedia. Newcomers to a discussion community can easily see practices and norms at work, because the process and the results are the same thing, and are completely transparent by definition. Since much if not most of the process of writing Wikipedia is reorganizing and rewriting and cutting and polishing, without any one user having responsibility for an article, it’s not obvious just quite what contributions are most helpful, or even helpful at all.

I think the feedback (reversions with edit summaries, discussion on talk pages, comments on users’ pages) are okay, but it’s an inherently different kind of feedback than you’d get from, say, HN or Facebook or Twitter or Stack Overflow. Just comes with the territory.

I think Wikipedia could do a lot better, especially if it had more programmers working on technical improvements. But I wouldn’t guess the systems used by discussion-oriented communities could be usefully easily transferred.