There is a good selection of emojis to include in Teams Messages. However, the set of emojis that is available to react to messages by others ('Add reaction' button) is limited to seven types only. For example, there is no 'thumbs down' emoji to signal disagreement. Could the 'Add reaction' set be extended to the same set available for in-message text, or could it be made possible for users or Site Administrators to extend the 'Add reaction' set of emojis?
We offer limited set or reactions because:
1. we don't want to overwhelm users with lots of emojis to pick from when reacting
2. as part of expressive messaging, we are making reactions animated (you should see it in our June release). We cannot make the whole palette animated :)
Offering a limited set and making them very expressive is the decision we have taken for reactions.