Podcasting Chat Community

@scottjenson I think that PMs should lock to who they are initiated with. That means the people tagged for that conversation when the PM is initialized are the only people who can be in the conversation. Further mentions *must not* expand the group.

I don't know if that means you should break the ability to do a private reply to a public message, but UX wise it might make sense to do so.

@scottjenson I think it would be fine, but I guess you'd still need to solve some design and architectural questions up front if you *know* you're going to do encryption in the end.