Should comments like "please add details of X to your answer", "done" be flagged for deletion?
Deleting them would improve readability of the thread. The answer-relevant information they contain is already in the new version of the answer. If someone is curious about the edit history, they can click on the edit history.
(X is something that only the answerer, not the first commenter, knows the details of. Otherwise the first commenter could have edited the answer.)