this is just false. Purple community will literally be a relay and we will build ui support for this so that anyone else can run a community this way. In the purple case it will be public read and private write, but making relays first class in app (only show posts from a single relay when you click on it) is the most important thing to make this work. Some people try to do this already but treating relays like a commodity and spreading the same note everywhere is killing this use case.