This is a quote from the book "On Zero Confirmation Transactions" by Chris Pacia
...ansactions containing a sequence number less than the maximum. Technically, retailers will be able to detect unconfirmed RBF transactions and reject them (making the fee bump part of it useless) . So, at least in theory, the opt-in shouldn’t totally destroy zero confirmation transactions. But the intent is clear. The goal is to eventually eliminate the opt-in part, this patch is just to get the foot in the door.

Once zero confirmations transactions are totally destroyed, you will only be able to transact with a retailer by using one of the quasi-centralized, thi...
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