I don't really know what I'm doing, but. Why couldn't messages be stored encrypted on a blockchain with a system where both user's in a one-one conversation agr

I don't really know what I'm doing, but. Why couldn't messages be stored encrypted on a blockchain with a system where both user's in a one-one conversation agree to a key, or have their own keys, that grants permission for 'their' messages. And then you'd never be locked into a private software / private database / private protocol. You could read your messages at any point with your key.