This would require some kind of federation alliance of instances that check each other’s usernames to ensure no duplicates over the whole network. Sure, maybe lemmy.shit doesn’t recognize the network, but then they don’t get federated with.
This is definitely possible, but it doesn’t seem to be happening.
This is a process known as proletarianization. It happened to the artisans when we moved to industrial manufacture, it happened to the pastoralists when we moved to factory farming, and now they can finally go after artists and techs and editors.