Facebook's Messenger—which recently introduced Messenger Day, a share-your-life feature akin to "Stories" as seen on Snapchat and Instagram—is adding two additional capabilities aimed at optimizing the service for group conversations rather than just chatting with one friend at a time:
• Similar to their counterparts in Facebook's own app, reactions let you quickly respond to a specific message with an emoji-like icon, representing "love," "smile," "wow," "sad," "angry," "yes," or "no." (That last one isn't available on Facebook itself.)
• Mentions let you reference friends by typing an @ sign and their user name, just as you can on Twitter and Facebook. If you do, they'll receive a notification so they can join the discussion.