Twitch updated some new features for in-game chat. You can now send private messages within chat across channels, for example if you are watching Summit1G you can send a private message to your buddy watching itmeJP. Only you and the user you are whispering to will be able to see the conversation.
For more instructions on house to use the new whisper feature, take a look at the instructions below and over to the Twitch Blog for more information.
Simply type /w [username] into chat to send a whisper to any online user with the appropriate whisper settings. The username will autocomplete with the last 5 users you’ve whispered to or received a whisper from during that particular chat session, or you can type a complete username.
via Twitch Blog
