This question has been an issue for Canvas users since 2017
I have used Canvas previously as a TA and now as a professor, and it is absurd that you still can't delete saved comments in an assignment rubric.
If I want to reuse a rubric rather than create an entirely new one, and I edit one question, there is no way to remove saved comments that have been made irrelevant and/or incorrect? That is ridiculous.
Fix this issue, please. Make a feature. The comments are clearly stored somewhere... give users access to them so we can remove (if not edit) comments that are erroneous, redundant, etc.