On Mon, Jul 31, 2023 at 01:26:11PM +0300, Daniel Lipshitz via bitcoin-dev wrote:
> This would unnecessarily and extremely negatively impact merchants and
> users who choose to accept 0-conf while using mitigation tools like GAP600.
> This negative impact could be avoided by simply adding first seen safe rule
> - ie a trx can be replaced but needs to include the original outputs.
> 
> At GAP600 we continue to see strong use of our service for BTC we have seen
> circa 350k unique trx hash per month (over the last 3 months) requested to
> our platform. Our clients include - Coinpayments, Coinspaid and Changelly.

I checked, and Coinpayments and Coinspaid are both merchant processors. I could
not find any example of actual merchants using their platform accepting
unconfirmed payments. I also could not find any documentation on their websites
indicating unconfirmed transaction acceptance.

As for Changelly, their website says right on the front that "With an average
transaction speed of 5–40 minutes, we ensure you can swiftly take advantage of
market opportunities." Obivously, 5 minutes is not an unconfirmed payment.

Additionally, I verified myself by doing test transactions with BIP125 disabled
and an adequate fee: unconfirmed payments are not accepted by Changelly. As
their exchange flow clearly says "Once BTC is confirmed in the blockchain,
we’ll start exchanging it to <coin>."

You need to provide an genuine example of an actual merchant who accepts
unconfirmed transactions as payment, and actually relies on first-seen
behavior.

> We have not seen any impact of full RBF on double spend rates for our trxs

Based on the above findings, this appears to be because you don't actually have
any clients who rely on unconfirmed payments.

-- 
https://petertodd.org 'peter'[:-1]@petertodd.org