It points out that the use of SIGHASH_NOINPUT in the protocol means the nSequence field is not included in the transaction signature, which makes it susceptible to malleation. Additionally, the email clarifies that update transactions within this protocol are designed in a way that requires the output amount to be equal to the input amount. Consequently, fees cannot be deducted directly from the channel funds during an update transaction. Instead, the cost must be covered by an external Unspent Transaction Output (UTXO), which is typically provided by the party initiating the closing of the transaction. This explanation is crucial for understanding the technical nuances of the DRo protocol and its implications on transaction fees and channel updates.