This item is still on the backlog.
Adding any emoji as a reaction remains under review.
I am marking this as partially done to let you know a new reactions bar with Like, Heart, Laugh, Surprised, Sad, and Angry has begun rolling out to all users.Ryan Ersland commented
This is my top feature request. As a frequently remote employee at an organization that previously used Slack, I feel that reactions are invaluable. They provide a low-stakes way to participate in a conversation without the visual disruption of a new post, playing a roll similar to body language in a face to face conversation. A rich vocabulary of reactions is a critical ingredient for bringing meaningful human interactions and team culture to a platform like Teams.
I'm glad to hear that you're making progress! You'll make a lot of users like me very happy when this becomes generally available. 🏆
We’re currently working on defining a compact mode experience. I will post more details when we have more to share.