I legit had a freak out when no one could post in any forum (including me) and I was unable to change permissions despite BEING AN ADMINISTRATOR.
Come to find out, when I moved forums from the one single category I had previously made to now be category-less, it converted them all to categories. Of course NOTHING communicated this. All I saw was forums that, regardless of being a child of what I explicitly made a category or not, could no longer have any permissions changed aside from "See Forum" (which calling this a forum adds to the confusion).
There's no reason to force categories and absolutely no excuse to auto convert types without consent. While seemingly minor, this really harmed my perception of reliability in this product...