[jooize]

I consider that argument unpragmatic. Any recipient can still be made in control of keeping messages they have received. Sender must assume that the message is unretractable, because recipient can record it with a capturing device. If there is zero trust, you must operate by that assumption. If there is non-zero trust there are practical benefits to enabling any party to request the deletion of messages. Whether each party will accept that request is a matter to consider by the sender. Deletion can be per-conversation or per-contact preference controlled to automate, disable entirely, or prompt.

The program can not guarantee deletion, but in practice that is not necessary for it to be useful.

[JoshTriplett]

I'm not arguing that it is impossible to provide a best-effort mechanism. I'm arguing that it's a bad idea for a messaging program to even consider accepting deletion requests by default, because it sets unreasonable expectations.