Subscribers-only chat

Switch it on and only accounts subscribed to the channel can post. You choose how long they must have been subscribed, which is the part doing the real work, since a raider can subscribe in a second but cannot fake having subscribed a week ago. Viewers still see the chat, and they are told the restriction is active and what the requirement is. It can be toggled before or during a stream or Premiere, so plenty of creators run open chat until trouble arrives and tighten it then. The cost is that first-time viewers go quiet, which matters more on a stream carried by a handful of talkers.