Satoshi recognized that replace-by-fee was a
very bad idea (
except where the inputs and outputs were unchanged).
Additionally, he understood that each node accepting the tx it sees
first is a key concept in the distributed consensus mechanism:
December 09, 2010, 11:58:54 PM:
...
There would need to be some changes on the Bitcoin Miner side also, to make the possibility to accept a double-spend into the transaction pool, but only strictly if the inputs and outputs match and the transaction fee is higher. Currently, double-spends are never accepted into the transaction pool, so every node bears witness to which transaction it saw first by working to put it into a block.
...
(emphasis mine)