I haven't seen this argument for RBF/full-RBF being discussed:

An attacker sends a tx (T) to a merchant and at the same time sends a double-spend tx (D) to the rest of the network, hoping that D will prevail, except on the target node.

If T is not replaceable, the merchant will not become aware of D until D is mined.

1/n

If T is replaceable, the merchant can wait X seconds before sending the good or service. If no double spend has happened within X seconds, they can be pretty sure that this particular attack isn't being pulled off.

Has this been brought up as an advantage for RBF/fullRBF before? I'm looking for links to such discussions?

2/n

A typical attack that utilizes RBF is to send the replacement transaction right after the good or service is delivered. This makes for a window of failure for the attacker. The longer delivery takes, the higher the risk of attack failure. The merchant can thus wait X seconds before delivery, to somewhat deter attempts at this attack.

With the attack descibed above, if D is successfully propagated to miners, there is no risk of failure if T isn't replaceable. So the problem boils down to how to get D to miners, before the merchant's node propagates T to said miners. On the other hand if T is replaceable, the merchant will become aware of D within the time of normal transaction propagation.

@pete @harding any thoughts on this?

4/4