To mention someone and notify them on a comment, simply:
- Click anywhere on the frame to add a comment
- Enter @ along with their name in your comment
- Type in the rest of your comment
- Click post now to post you comment
The person that was @mentioned will instantly receive an email notification with the comment itself and with a link to the frame you commented about.
Mentioning is possible only for users within your discussion group. If you want to mention a user that isn't part of your group, add them to you discussion group first, then @mention them in a comment.