Could we implement a banner for a sold account? So like the one that says "This users password was changed recently", it could read "this account was sold recently". Of course some account sales are undercover, but it could just be a box that admins could tick if they knew of a sold account.
Unenforceable. 99% of accounts get sold behind closed doors and for this exact reason. If you're dumb enough to publicly state it's a bought account then you'll likely get tagged with negative feedback anyway.
I concur. How exactly do you confirm the the account is sold (in some cases it works, but it will not work in all cases)? Is it because my IP has changed in addition to password/email? The last time that I've done a password/email change I've also changed the VPN that I'm using, for example.
I've been applying a red tag on sold accounts or buyers or sellers of accounts for a year now.
I think that is appropriate, especially if the accounts have previous positive trust (especially from DT members).