Probably using `lino.modlib.comments`. Comments (other than chat) means that you don't address a particular person. All users who starred a ticket would get notified. The comments plugin needs one more model `Notification` so that Lino knows when a comment has been read by a user.

(Maybe later: Replace the ticket description by a "primary" checkbox on a comment. Advantages: many tickets don't have any description (saves screen space), possibility to switch ticket descriptions.)