I’ve started looking into this for my discourse, and am struggling a bit to understand what features are provided now for category-specific moderators. Am I right that at the moment it’s simply a category moderators listing on the about page and access to Category Group Review/Moderation? In my testing I have not found any other handy functionality, like whisper access.
Would it be possible for someone in the know to create a #howto topic on category-specific moderation and keep it up to date with the latest functionality provided? I’d be grateful. 
FYI this link in the OP seems to be broken.