When clicking on a username in chat, see which channels you both follow
Similar to Twitter, so when you click on a user's name in chat you will see:
A "follows you" tag so you know if they are following you, if you happen to see them in another channel's chat
An option to view "channels you both follow" so you know if you have any other channels in common
People often say they see similar names in other chats and it would be really useful to know what channels/interests you share with other Twitch users.
Great idea. Like you say - much like Twitter.