Have you ever transferred BTC from your coinbase account to a LBC account? (this includes either a direct transfer, or a tx from coinbase to your wallet and then using an address spendlinked to the address you send the BTC from coinbase to LBC?
When you would buy BTC on coinbase and then transfer it to cold storage, when you decide to sell those BTC, would you use the same inputs that are from coinbase, or are the inputs that you use to deposit BTC back to coinbase from other sources?
No I have not.
Maybe minimal additional inputs that I got from my dad or bro, but even those they initially got through Coinbase.
Well if they don't want my [legitimate] business then I'll go elsewhere. Any other reputable American bitcoin brokers out there that y'all would recommend?
If you received BTC from your dad or brother who also purchased BTC from coinbase then they may think that you are in control of their accounts and this may be behind the question of asking about other coinbase accounts that you have.
If this was their thought process, then they might be afraid that you were using multiple accounts to get around their daily limits, which could potentially expose them to additional credit risk.......this is of course speculation.