Just 2 days ago we desperately needed an unsend function. We had a support case where it wasn’t clear from the explanation what was going “wrong”. After confessing that it is a bug and then sending the reply, we quickly realized that there was another way to view the issue outside of the user’s description of it. Then we realized that it wasn’t a bug but that the user misinterpreted what was going on.
Unsending would have helped avoid the mess that resulted. The case was for a larger client who regularly contacts support and in this case, was in contact with a new face that we’d like existing clients to trust as one of our experts.