Quote from: autumnraynefyr on November 29, 2015, 07:14:48 AM

Multi address wallets like Electrum would make this a hassle and probably actually push away potential buyers as if I remember correctly, each wallet can have as many as 3000 addresses, and if there are amounts all over in the wallet, I dont think someone will want to provide 30+ addresses to verify their funds..

Transfer all your Bitcoins into one wallet and use it. I doubt anyone would have lots of change even with HD wallets, change are also used when sending transactions. If there is indeed lots of different change address, transfer them into a single address and sign from there. It isn't hard to do.

This would only work if the user's wallet service/software allow users to sign message. Some shared wallets do not but some do, like coinbase.com. In that case, you need to ask the person to transfer them into an address which a signed message can be generated from.