This would be something theymos could create: a new rank that shows you're an old user, without disclosing your old account.
If Admin only creates such accounts for users who made a name for themselves, it could be a solution to have and eat the cake!
I too wouldn't mind having more privacy, but once it's gone, there's no way to get it back.
That would be something, but if your new rank, for example, shows as "New Legendary" instead of just "Legendary" then that new account get's "noticed" as well, and some internet detective is going to connect the dots. Anything but the original rank is going to arouse suspicion.
Let's have a thought experiment:we already have Bitcoin mixers. What if we would have a Bitcointalk Account Mixer?
For the sake or argument let's assume there are 8 people with more or less similar accounts (similar Rank, similar Trust, similar language). Those 8 account owners would all exchange their account in a big random shuffle, where none of them knows who gets which account. Their feedback can get a bold marker stating the date of the account shuffle, so it's obvious the older feedback belonged to a different person.
Of course, this isn't ideal: the post history for instance suddenly doesn't belong to the person anymore. But the most important argument against account sales won't be a problem: none of these people would have an increased reason to start scamming or spamming with the "new" account.