Attendee comment emails

Is there any way that comment reply emails could only be for active attendees? If I have a course up and someone comments, I want them to know when I’ve replied. I also don’t want them to receive comment emails from others who attend after them in response to their comments. The content may be useful so I don’t mind their comments staying up for others to see even once they are done and not signed up anymore.

Or, perhaps is there a way where only the attendees and presenters can comment to each other and other scan only view?