> An element of a distributed system that wants to debit from bank accounts must acknowledge the receipt of a message after making its effects durable. I do n

> An element of a distributed system that wants to debit from bank accounts must acknowledge the receipt of a message after making its effects durable. I do not and never have disputed that. But I fail to see what that has to do with the matter at hand, namely, whether or not exactly-once delivery is possible.