I think we should distinguish between "rooms" and "threads" at the database/object level. Although these will be 99% identical, I think they have enough differences to justify making this a formal flag. In particular:

• When browsing rooms, we shouldn't show you threads (or, at least, there should be options to show only rooms).
• Threads should have all policy settings locked to "members" of thread.
• We might want to customize UI strings, e.g. "retitled this thread" vs "renamed this room".
• We might want to customize other UI stuff, like switcher icons.

To support this:

• Add an isRoom (or similar) flag to threads.
• BOOM