Various thoughts:
Seems like Intl deserves a category.
For proposals, I think we already tend to view them as implicitly grouped so it's probably a matter of making those groupings explicit. OOP (or Classes) and RegExp seem like good, clear ones. Built-ins might be a bit too coarse-grained, but then I'm also not certain how granular we want to get.
I was going to say Annex B too but I'm not sure whether this is the place we expect to have such conversations.
I think a category for assistance with spec-reading might be cool? Not sure what we'd call it; How Do I isn't quite right and Does This Mean What I Think It Means is too long. 