Can I mention someone in a comment?
Yes, you can mention someone in a comment by typing @ followed by the person's name. Use the autocomplete popup to make sure it's the right person you mention, and type Enter or Tab to complete the mention.
Alternatively, click the "Mention" link below the comment. When you mention someone, the person will get a notification that you mentioned them (unless they've disabled this).
You can also mention a team the same way. Each member of the team will then get a notification that you mentioned their team (unless they've disabled this).
You can also mention backlog items, tasks, sprints, and releases, as an easy way to include a reference to these in a comment.