Split "send message" permission into "send message in main room", "create thread", "send message in thread"

[Nostramadeus]

In a room, it seems you can only allow someone to send a message, or not. But I'd like to separate that with sending messages in threads. This way we could simulate a forum or announcements room much easier. I want to let mods be able to send messages in the main chat and every participant able to start a thread based on a message and chat in the thread

Perhaps it should be split into three: "making a thread" and "chatting in a thread" and "chatting in the main room"