For A LOT of our courses, we have instructors who require students to post an original reply to the instructor's discussion and also respond to two or more of their fellow classmate's responses. It would be helpful to have a way to close off responses to the instructor's post, but keep the discussion open for students to continue replying to each other for a separate amount of time.
Example of this would be: You have until "this date" to reply to the original post, and then until "this date" to respond to two of your classmates.
As it is right now, if we extend the available date, the entire discussion is open. Also, we want the students to have more freedom to choose who they can reply to, rather than assigning them peer reviews.