Is Sarang a complete idiot?

[humanoid]

I can accept that we are two individuals with the same memories, with equal and non-exclusive claim to my identity. If I do accept this, I should be pretty safe in assuming that my identical copy will feel the same way.

You did read my last paragraph, right? (the one before the PS)

"pretty safe" is not 100%, your copy is not you anymore after a certain point (that is definition dependent as I mentioned in the PS) , you even said it yourself

the act of running a brain scan is simply creating a brand new life, albeit with a full set of previous memories.

This brand new life will certainly not experience the same things you do after the scan, it could get to a point where it might question your previous decisions, including the one not to kill the other you (which is actually pretty likely in a messed up environment like Pathos-II).