That's why we disabled the buy-sell-trade community on our niche instance. Nobody got scammed during the short time it was open, but if a username can be duplicated it makes scamming that much easier.

Uhhhhh. Yeah this was always something I was worried about with multiple instances. Having multiple usernames run my different people. The @ at the end will be crucial for people keep them separate

You could always message an admin and ask them to transfer the account to you.

The only bad part about the fediverse, imho, it’s hard to be the only one with your username. What makes it bad is a malicious user, that you may have pissed off somehow, start using your username in a smear campaign to hurt your reputation.