It would be really helpful to be able to edit comments once posted. Sometimes, you think of a better way to express what you have just written and it would be more efficient to just edit the comment already posted, rather than reply to your own comment to add the new/adjusted info.
Here's a use case scenario:
It would be great to allow users to edit their comments. It’s VERY VERY easy to post a typo or to write a sentence that isn’t quite grammatically correct. Students are often told that they are judged (and assessed) by their communication skills, including grammar and spelling. So it would be fair to students to allow them to fix these errors as this could have a serious consequence to a tutor’s assessments of their communication skills.