That was the problem elsewhere (non-Discourse community). I contacted them and they said they refused to go and delete the PM because they didn’t want to breach privacy. They even told me to use the ignore feature of their system if I didn’t want my accidental recipient to contact me back if I feared I would be flamed. I immediately sent an apology PM and thankfully the other person took it and didn’t broach it anymore. I got lucky. Knowing that community it could have been a lot worse and I would have had to use the ignore feature.
I, as an admin on my own community, have deleted PMs within an SMF database if the sender immediately contacted me and I knew by “last seen” records that the recipient didn’t read it. It’s prevented feelings of humiliation, extreme awkwardness or outright drama. It doesn’t happen a lot but when the mistake happens it’s not pretty if there’s no way to pull the message immediately.
That sounds best. If the admin can edit the email window in the admin CP separately of the edit window then that would allow me to set it longer and give time for the recipient to self-delete if they feel they made a mistake.