In the spirit of eating our own dogfood, we at Discourse use Discourse as our internal KB. It’s part of the same internal-only Discourse that we use for discussion of “everything else” that can’t be public (what to do about the gopher problem in the crawlspace, that kind of thing).
Our categories (and sub-categories) are more-or-less along the usual “department” lines: ops, dev, biz, gophers, etc. As far as settings go, I don’t think we do anything particularly different to what any other Discourse instance might have. One thing we do use fairly heavily is comment deletion. While plenty of comments do get left on KB topics, if the “main article” is edited to incorporate (or otherwise “handle”) the contents of a comment, that comment will often be “nuked”, just to keep things clean. So, you’ll want to give everyone sufficient powers to be able to do that.
Depending on the past experience of your team, you may need to reinforce that editing the main article is not just permitted, but in fact encouraged, by everyone on the team. For people who are used to forums, but perhaps aren’t quite as used to wikis, they may feel that etiquette demands that they not modify “someone else’s” post, but instead make a comment. The best analogy I can make there is that handling your KB like that would be like trying to build software by applying every diff file every time someone wanted to compile it. Madness.
One thing that does get in the way a little bit is “superceded” topics. While we tend to “edit in” changes to existing topics, there are occasions where it makes more sense to “shut it down” and start again with a new topic. In that case, the “old” information is still sitting there for anyone to stumble across, amongst more relevant search results. You can edit the title of the old topic to flag it as “out of date”, but @sam has plans (when a future shipment of round tuits comes in) to “weight” topics in the search results, to deprioritise (or hide completely) topics that are marked as “superceded”.
Hope that helps. Feel free to ping back with any other questions or thoughts you have. Knowledge management is a bit of a passion of mine; comes from being married to a librarian, I guess.