I wrote a long reply (1.2k+ words) to a moderator message, and after clicking "Reply", I spotted a typo, just one typo.
Given that moderator messages are private and cannot be edited (by others), it would be useful to give users a grace period of 5 minutes, just as it is everywhere else, for users to edit the reply after sending it. It's not like spam or other inappropriate content where a grace-period edit would be harmful (e.g. make existing flags confusing) so I think it's worth it.
Can we have a grace period to edit moderator messages, both from mod to user and from user to mod?