When you watch a stream with thousands of viewers, I'd like to be able to chat with users easier, but it scrolls by so fast that it's not even worth trying. My idea is to have a breakout window. If you get @mentioned, it goes in that breakout window. You could also just add users to that breakout so you'll always see what they are typing. It would make chat for large streams better. Also, if you have to look away for a second you won't miss anything.
This is very useful to allow people to actually be able to form connections over the Twitch platform. Kind of how Outlook works, you can view emails that have @mentioned you specifically so you can reply at your convenience.
Especially for Twitch streamers it might be useful.
If the chat gets too filled for a popular user - you can have a "clear messages" area.
Perhaps subscribed users can have access to @mention a streamer to keep their messages not lost in a busy chatroom.
But from the perspective of regular non-streamers - it would prove to be useful non-clutter way to let a conversation continue.
This message sent via @Message will still be visible to all users- but it's filtered enough where two users can see previous messages tagged to each other to continue a conversation smoothely.