To mention other users in your comments, just add @ followed by the name of the person you’d like to mention.
Whenever you type in the “at” sign, a list of users in your organization will load.
From there, you can select the right person or just continue typing their name and press Enter to confirm your selection.
People who are not on the board will also be listed and marked (if the board is public, they will get access right away, if not— share the board with them to make sure they can view the comment).
Comment list and mentions
The comment list will also mark the comment thread where you’re mentioned with a red @ sign.