> What a bank can do for "free" (really just very low cost) in fiat would compete for scarce transaction slots in crypto. This doesn't seem to be the problem.

> What a bank can do for "free" (really just very low cost) in fiat would compete for scarce transaction slots in crypto. This doesn't seem to be the problem. If 1% of transactions need a second transaction to reverse them, we can amortize this cost over all transactions and say reversibility adds on average 1% to transaction costs - hardly significant when choosing a payment mechanism. Reversing significantly more transactions than that isn't normal. If you try to reverse 10% of your credit card payments, you'll soon need a new credit card issuer.