Regarding "Talk" -- from a UI perspective I think it is one of the worst things about mediawiki. I think that Drupal's stock comments implementation on the same page as the node is much better than having a talk page on a separate page.

We may have to disagree here. I think of the "talk" page as a place for meta-discussion--discussion about an  article, say, if we were to use the MediaWiki example. I would want "comments", were they implemented for a page (MediaWiki doesn't do this, presumably on the assumption that non-meta comments belong as edits in the article) to refer to the =subject= of the article.

So, if I write a page on klezmer, and you make some edits with which I disagree, the "talk" page is a good place to hash out administrativia, but if you and I have different views on klezmer, the "comments" section would be a good place for the two of us to discuss (along with anyone else who joined in).

Does this make any sense?