I'm not sure where in that article the re-write-microcode feature lies? That is, modern CPUs can write microcode for instruction sequences, not just single opco

I'm not sure where in that article the re-write-microcode feature lies? That is, modern CPUs can write microcode for instruction sequences, not just single opcodes. Which is almost exactly what a compiler is, if you substitute 'op code sequence' for 'source code sequence'.