Just so you all sig spammer know, selling account is allowed here. At least I tell you the account so you know that what kind of things you are buying and not just some spam account at games and rounds.
From what I understood, they are interesting with your account but they don't want to buy it and recieve a negative trust later which will affect their chances to be accepted in the signature compaign.
That's why they told to hide its identity.
You can see others posts here to get further information.
Good luck.