This is currently possible. Here is some information
how to mention people in shared messages in the activity stream but the same is valid for comments. In general, if the user will receive a notification or not depends on the user's personal notification settings (Settings -> Profile -> Notifications). By default, the notification for "Someone mentions me in a comment" is enabled so if the people didn't disable it explicitly, they will be notified.
I hope this will suit your needs. Let us know if you need more assistance.