Can I comment on a completed interactive assignment?

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I use interactive assignments. I know that while the assignment is open I can communicate as the "teacher" back and forth with the user. I "grade" them when users submit them and that closes them out. Once the assignment is closed is there any way for me as the administrator to add additional comments either to myself or the user on an individual user's completed assignment, such as note that maybe I should follow-up on something in 6 month's time?

Thanks.