Being able to unsubmit homework and then resubmit it after fixing your mistake.
There is a popup that asks you if you are certain you are ready to submit your homework before actually submitting it. This prevents you from accidentally submitting it. Grading would take much longer if students were able to submit something, then take it back and resubmit it and you have plenty of chances to fix it before you actually submit it.
I've gotten the pop-up but I clicked cancel. But it still submitted. TWICE
Customer support service by UserEcho