Yes, you can easily tag users via the @ symbol such as @USER-NAME.
You can also tag the project team with @Project, the whole workspace with @Workspace and whole teams of your workspace with @YOUR-TEAM-NAME.
Mentioned users are automatically notified by awork about your comment (depending on their own notification settings, e.g. by e-mail and directly in awork).
If a user does not have access to the task or project, she/he will not receive a notification. If this is the case, a small notification will appear after your comment post.