Thanks for flagging ​@Jef Vanlaer !  You just made me aware of a platform quirk I’ve never come across before.  It looks like even if we disallow category ‘visibility’, you still see it in the list when creating a topic if other permissions (create topics or replies) are enabled.  I would expect ‘visibility’ to totally lock a category down, but apparently it doesn’t work like that.  

For the groups it’s different, as the idea is that you can post in a public group even if you haven’t officially joined it yet.  

I’ve adjusted the permissions for those two private categories, so you shouldn’t run into them in your list again.  :)