If you would like to keep a pm, you keep it in your box or even better, archive it to make some space for more.
If you wouldn't like to keep a pm, you just delete it.
I don't see why you wouldn't take the decision above right away and wait for let's say 3 days (i.e.) if this feature would be added.
Voting no, as i don't really see a use for it

.
This post was edited by Kafir on Apr 23 2020 07:17pm