Possible suggestion for FAQ 101

Do any of the FAQs for communities actually state that communities can't join other communities? A support request this morning brought the issue up, and a quick search of the FAQs yielded no mention of it (unless I'm blind, which is always a possibility). FAQ 101 would be the obvious location. Maybe add "Only personal journals can join communities. A community journal cannot join another community." to the end of the first paragraph.

Or whatever seems best. If that update is made, is it worth adding another line about how it used to be possible for comms to join other comms, just not anymore? That's what Support often sees--"blah is a community and is a member of the dee and foo communities, how do I do that."