Facebook has made quite a few tweaks to Messenger, with reactions and @-mentions added - you can now react to individual messages, or even tag a specific friend in a group chat.
When you're using Messenger, reacting to a message is as easy as pressing and holding a message to see Facebook's love/laugh/cry emojis to show up. A small counter will add up the reactions, showing you who exactly is spamming that emoji button - it even has its own notification on your lock screen, a nice touch by Facebook.
Moving onto the mentions feature, where you just need to use the @ symbol, and then Messenger will show a drop down menu of all of the people in the chat - you can then tag their name, and they'll receive an individual notification.
These new features should be rolling out to Messenger users now, and over the next few days.