In our Discourse forum, we have a few top level categories that exist to group their child categories. For instance, we have Feature Requests which contains Client/Studio/Web Features, Bug Reports which contains Client/Studio/Web Bugs, and Lounge which contains Off Topic and Platform Discussion.
The top level categories are locked because we had too many people posting in them instead of the appropriate subcategory – we would rather them guess which subcategory and get it wrong so their thread can be seen and moved versus posting in the top level and no one noticing it. The results of locking the top levels have been mostly positive, but we’ve also had an issue of users thinking the category is locked for them.
Instead of recognizing that there are subcategories to post in, they see the locked top level and think “Oh, I don’t have enough permissions to post feature requests.” I suspect that this is because the “New Topic” button is greyed out rather than the top level not appearing in the Create a new Topic category dropdown because the complains have always been “The category is locked”.
It would be nice if there was a way to communicate to users that a thread can’t be posted in because you’re meant to use its subcategories rather than them not having appropriate permissions. For instance, the ability to mark categories as top-level and have them show no topics in their list on Latest, but instead just a list of their subcategories similar to the category list.