Please consider adding the functionality that allows instructors to disable student comments on assignment submissions. Allow the instructor to decide when such comments are appropriate depending on the size of their courses, pedagogical setup and instructor-student ratio. At this time, students comments can be dealt with in the following way:
1) Via setting up personal notifications;
2) Via explaining how the communication flow works in the course.
None of these is very effective, especially with large enrollment courses, so allowing control would be helpful to instructors.