Reddit had the ability to have a per-subreddit wiki. I never dug into it on the moderator side, but it was useful for some things like setting up pages with subreddit rules and the like. I think that moderators had some level of control over it, at least to allow non-moderator edits or not, maybe on a per-page basis.

That could be a useful option for communities; I think that in general, there is more utility for per-community than per-instance wiki spaces, though I know that you admin a server with one major community which you also moderate, so in your case, there may not be much difference.

I don't know how amenable django-wiki is to partitioning things up like that, though.