It would be useful to be able to disable student comments on papers that I've graded.  I'd rather students communicate with me by email if they have questions, because it's easier to keep track that way.  I also comment extensively on papers and find that student responses tend to focus on explaining to me why they made the errors they made, which isn't particularly useful.  I've not had this sort of thing happen before and think the platform is set up to make students think they're being invited to explain why, for instance, they're writing run-ons or comma splices.  They don't need to explain; they just need to take note and correct the misunderstanding of, say, comma placement.