This was reported in the publication Wabetainfo. Recall that the messenger team has been working on the ability to leave reactions to messages for several months. Thanks to the innovation, users can put different emoticons on messages in the dialogue. This is done in the same way in the Facebook app.
It is noted that the function of reacting to messages assumes reaction notifications for individual chat streams, as well as group chats.
According to the source, the ability to notify users about reactions to messages will be released to all users as soon as the next update.