this is not about editing other people’s messages, but to point out to your chat partner when they did a typo, this is useful to use Delta Chat as a “language exchange” app where two natives of two different languages chat to practice and help each other to learn the language,
there are some existing apps for that but in my experience they are not great as the main focus is not the chat app itself, not to talk about security/privacy concerns and the fundamental flaw of not being open source and decentralized services not tied to phone numbers
here is an example of how text correction looks in one of such apps:
it is not the same, you are not editing the other person is message, which will stay there, you are showing a correction to the message, i guess it is more similar to reaction to a message in this regard, it is like attaching metadata to message, if core introduces a way to attach metadata to a message that would be good enough for me, then at least I could implement it in my own client
otoh, maybe the correction could be an independent message quoting the message it is correcting, so only a view type would be needed, I guess this is simpler as then you have a new message in the chat and not some kind of hidden up where the original message was sent, I don’t remember well but I think this is how the app in the picture works