It's the tag(s) that would send a new thread to a virtual section, is that right? And is it only the original author who can assign the tag(s) to their thread? Or can anyone assign a tag to a thread and send it to their own private virtual sections? And what if the author does not assign a tag to their thread?
Those are all good questions.
If everyone is allowed to assign any topic to any virtual section, we would end up with a big mess. And if only authors are allowed to assign their own topics, then no doubt a lot of topics would remain unassigned.
But then, not every topic needs to be assigned in the first place.