That is indeed getting close to what i have in mind (“subforums” has been the goal). Thanks. I’ll look more into multisite.
I would have thought that allowing users to create their own sub-site in a multisite structure would be a fair bit more resource intensive than, say, allowing users to create their own categories. Could a multisite work with hundreds or more sub-sites? I’m wondering how much drain that would be on the server, or perhaps its not much more drain than a busy single site?