LeanKit's step-by-step guide on using @mentions in comments to communicate directly with team members.
Collaborate More Effectively Using @mentions
In card descriptions, card comments, task descriptions, and task comments, you can “@mention” a fellow user. This will send a one-time email notification to that user with your comment or description text.
Simply type the ‘@‘ (“at symbol”), then start typing the first few letters of the user’s name. A list of matches will pop up.
Select the user you want to @mention from the list, then continue typing your text.
When you're done, click Post Comment to share with the tagged users.
You can easily view the comment history for each card at any time.