Redmine

I found the draft page I was talking about: http://gplv3.fsf.org/comments/gplv3-draft-3.html

This could be a good way to allow brainstorming/peer review within redmine. What I envision is more analagous to a Comment Tracker, similar to redmine's issue tracker (but not as complex). Comments would have an 'Relevant to' field which is the revision it was originally made on, and an 'Addressed in' field which tracks the version the point brought up in the comment was dealt with in. This way, the wiki page shows the current draft of the proposal all in one place, without having to read through lots of comments. Only the comments that haven't been 'Addressed' would still be shown in the current version, but you could use the wiki's versioning system to see how the discussion evolved along with the draft.

Or, perhaps this could be done within the issue tracker, so that comments can be hidden once they've been 'Addressed'.