I’m not sure what utility signing a message has inherently. You do this already behind the scenes on apps like iMessage or Signal with end to end encryption.[1] Or if you want to do it more directly but without the command line, there is Keybase: https://keybase.io/sign

Unless you were to upload each and every chat to a blockchain - which is prohibitively expensive - I don’t see the killer advantage over the previous alternatives. Also, many people here are also programmers, developers, and - surprise - hackers, so I am sure we would be interested in the mouth-watering use cases you’re thinking of (I looked at the Tweet thread you linked but it was just an explanation of public key cryptography in general.)

[^1]: Apple also refused to backdoor a terrorist’s iPhone at the demand of the FBI. OpenSea intervened when someone stole assets from a collector (https://blockzeit.com/opensea-nft-marketplace-stops-hacker-f...)