It would be nice to see an option to delete an already sent message on the remote device. Something that is also possible with other messengers. This could be realized by sending an email which contains a request to delete a specified message. Such requests should be processed with priority before new messages are displayed. In the case that the message has not been read already by the recipient, the remote device could send a confirmation of the deletion back to the sender. After that the message is removed from the sender’s chat as well.
you can not delete stuff on the internet, you can only ask people to do it, there is no “security that stuff gets deleted.”
Simon, you should read my explanation how it can be realized…
Such requests should be processed with priority before new messages are displayed
sounds like you want to rely on it… you should not.
We have a disappearing messages feature that also only works if both peers use delta chat.
Simon, you should read my explanation how it can be realized…
Anyways this topic was already brought up and discussed several times, so you “should” search a bit more before posting duplicates. 
Sure, it only works if both peers use delta chat. But in this case you can rely on it. With “priority processing” I mean the approach not to display the original message at all. It should be discarded on the remote client and removed from the server before the message is shown in delta.
Sometimes you send a message to the wrong chat. In this case it can be really useful to have such an option.