Hi,
I could provide signed messages but that would reveal the accounts and make them useless to a potential buyer. I'd suggest using a trusted escrow to confirm account details. All have neutral trust.
Given the nature of this sale a shill could be any account of any rank, however I'm keen to get some accounts of my hands as I've said before.
Would you be willing to stipulate that any sale would involve you providing signed messages to escrow after escrow is funded but prior to you receiving payment?
The BTC address that you sign the message from must be posted on an unedited post that is at least 6 weeks old. Would you agree to this?