Nodes default to full RBF these days. Miners run the latest node software. It doesn't matter what you as the merchant run. If the miners run full RBF (the default), the transaction still in your pool is not as likely to get mined as the transaction that replaced it that's in the miner pools. This is a new point @Hanshan raised that I had forgotten that I didn't raise. My points were valid anyway. Even if it wasn't the case, accepting 0-conf on Bitcoin is categorically worse in every way than on Monero today. That's the thing you're wrong about.