[Izkata]

I have no idea if this would work and don't want to risk messing it up for myself, but have you tried changing (one of) the account emails?

On the website go to the Your Account page ("Account & Lists" dropdown -> "Your Account" section -> "Account" link, which goes to https://www.amazon.com/gp/css/homepage.html ) and click "Login & security" to get to it. Same place you'd update your password/etc.

[endominus]

Maybe that would work, but I'm also concerned about messing something up. In particular, tripping some bot detection/account duplication algorithm and getting my account banned and all its content gone. I'll suffer the small annoyance rather than risking the black swan disaster.

[Reason077]

I wouldn't worry about that. I've had multiple Amazon accounts (with different emails!) going back many years. Never been an issue. They even make it easy to switch between them with the "switch accounts" function.