Bitcoin v0.12 introduces "opt-in" replace-by-fee semantics. This was an unfortunate political compromise as a result of situational context we are fortunate not to have to deal with. There is no such thing as optionality to RBF because there is no way to prevent transaction replacement in miner mempools. It is trivial to execute a double-spend even when the transaction being replaces is not BIP-125 compatible, and there are tools available to do this. Supporting this feature and advertising it is confusing and a potential source of security failures.
"Opt-in" RBF should be removed and replaced with full-RBF. We have no expectation of ever supporting zeroconf transactions at the settlement layer, and that is not changing.
Bitcoin v0.12 introduces "opt-in" replace-by-fee semantics. This was an unfortunate political compromise as a result of situational context we are fortunate not to have to deal with. There is no such thing as optionality to RBF because there is no way to prevent transaction replacement in miner mempools. It is trivial to execute a double-spend even when the transaction being replaces is not BIP-125 compatible, and there are tools available to do this. Supporting this feature and advertising it is confusing and a potential source of security failures.
"Opt-in" RBF should be removed and replaced with full-RBF. We have no expectation of ever supporting zeroconf transactions at the settlement layer, and that is not changing.