Users who receive the email get the subject line : New comment for [name of activity]
The body includes the comment

The user does know where this comment is being generated due to the lack of context. The user is forced to hunt for the activity name within all classes enrolled. Adding a placeholder / breadcrumbs / link to the activity in the body of the email can help the user link back to the activity where this comment was generated. (It could use the same treatment as grade modified/feedback emails)