The following scenario frequently happens: member $M_1$ answers a question, but he makes a typo that member $M_2$ points out. So $M_2$ leaves a comment, $M_1$ corrects the answer. If this correction is made when $M_2$ is not logged in, the comment may remain for a while (I personally have a lot of such comments posts, but especially when I play the role of $M_1$).
What I suggest is the following: in the same way as we can choose whether an answer is community-wiki or not, we can show whether a comment is NLR (no longer relevant) or not by picking a square, with the following features:
- the comment can be deleted by $M_1$ once the correction is done;
- it is automatically deleted after a while (for example when $M_1$ thanks $M_2$ for the edit).
It can also concern questions. For example when an user sees a typo in the question, or asks for a precision, which will (normally) come.
What do you think about this idea?