Reactions feature will allow users to express their feelings to each other's chat like the expression of emotion on regular Facebook posts. Special points are Reactions will only have 7 emoticons. which will include the most anticipated icon, Dislike emoticons.
The second new feature of Messenger is the Mentions feature. While chatting with a person or a chat group, you can type the @ symbol plus the name of another person to call them into the conversation as well as to let them know that this conversation is referring to them. , like the tag feature on Facebook. Of course you can also turn off notifications for that conversation if you feel the story is not related to you or feels troublesome.
These two features will appear on Messenger's new update in the next few days.