One of the only things I like in Microsoft Teams¹ is that I can edit messages I have sent.
I often send something without noticing all the typos and spelling mistakes I have made. I have tried to be more careful, but for some reason my eyes and brain prefer to see the errors after sending.
I asked about support for XEP-304 on the jabber.el mailing list.
And then I wrote a little jabber-last-message-correction.el, which implements rudimentary support for editing the last message sent, and also shows when an incoming message is an edit of a previous one.
It feels like I am the only one using jabber.el. But after I asked if I was, two people have said they use jabber.el too, so that's good!
¹ Don't ask.