This is a pretty good argument to not go in 'guns blazing' tagging every sold account because, according to threads I have seen in Auctions, both email addresses and private keys are being sold with accounts, making it very difficult, if not impossible to tell when an account has changed hands.
Sadly a signed message isn't definitive proof these days, but it's better than nothing, especially as not being able to provide one is a huge giveaway (though not exactly definitive in itself either).
Well, I can't wait for the day that someone buys an account with a private key and then the seller recovers their account back, leaving the buyer high and dry. The seller may even get lucky and be able to recover the e-mail account too.
[img height=150 ]https://media.giphy.com/media/pUeXcg80cO8I8/giphy.gif[/img]
It is interesting to see that you are hoping that a certain group of people will get scammed.
This has been noted.
I don't think he wants this to happen but this is obviously just a way to test the validity of that address. If someone else owns it then that user would be very reluctant to send money to it as the chances the money would disappear would be very high, though obviously he was being factitious, but I suppose you could say it was the users fault if he did in fact lose his money this way.