No domain separator for signed message

In SponsorshipPaymaster, the hash of the data is calculated as such:

function getHash(/* ... */) public view returns (bytes32) {
	//can't use userOp.hash(), since it contains also the paymasterAndData itself.
	return
		keccak256(
			abi.encode(
				userOp.getSender(),
				userOp.nonce,
				userOp.initCode,
				userOp.callData,
				userOp.callGasLimit,
				userOp.verificationGasLimit,
				userOp.preVerificationGas,
				userOp.maxFeePerGas,
				userOp.maxPriorityFeePerGas,
				block.chainid,
				address(this),
				paymasterId,
				validUntil,
				validAfter,
				priceMarkup
			)
		);
}

There is no domain separator in the signed message structure. Therefore, if another protocol had a signed message structure similar to the one in this message, then there could possibly be a replay attack.

However, due to the inclusion of chainid in the hash, cross-chain replay attacks are mitigated. Additionally, the data includes many unique parameters, such as initCode, which holds bytes for the construction of the account contract; therefore, it is highly improbable that a collision may occur.