Follower only chat
Restricting the chat to "followers only" would be extremely beneficial to removing trolls, unwanted raids, and unwanted attention. It would also heavily encourage follows.
Currently there are no bots that allow for this either, so why not make it a native feature?
I realize that followers only can be rather limiting, but this suggestion was actually from someone who is "HUGE" on twitch and gets hundreds, if not thousands, of people chatting at once. They are able to (somehow) limit it to followers only to stifle the spam to an extent. Their reason for not wanting to try Mixer was that this feature didn't exist.