I personally am using my iPad/iPhone (in the non-mobile-site view) about 75% of the time that I am on a SE site and therefore misclicks are frequent. I often click close/flag just to see certain info like which questons are the target of a duplicate flag (I believe the FAQ even suggests that you view close reasons in this manner). I often fat-finger my iPad/iPhone which has resulted in accidentally flagging 1 or 2 posts. Please implement this feature (but of course only for flags that are still "Waiting for review")!
This would also be useful for posts like this: Download a file part by part in Python 3 which I flagged for indicating it should be a comment, but then the answer was edited to include actual content, invalidating my flag (in my opinion) but the flag is still waiting to be reviewed and I cant "revoke" the flag.
