> (RBF). If the sequence number in a transaction’s inputs is lower than the max (0xffffffff-1), then …
“the max” is 0xffffffff, not (oxffffffff-1), so your statement is off by one. Both 0xffffffff and 0xfffffffe are possible non-RBF sequence numbers, with the latter meaning that the nLockTime is to taken notice of.
> the Lightning Network (which doesn’t reduce the pressure so much as relegate high fee transactions to the “blockchain-as-a-settlement-layer”)
Is this also a typo? I think you mean it relegates *low* fee transactions to using the blockchain as a settlement layer. High fee transactions will be able to continue using the blockchain as they currently do.