You can add an Emoji reaction to stickies to respond to any note. Emoji can be used for various purposes: voting, checking off to-do items, and just for fun.
To react with emoji, choose a sticky note and find Add Emoji in the menu. Selecting an emoji will place it on the bottom of the sticky note. It is possible to add votes to the existing emoji and add several reactions to one sticky note.
Reacting with emoji