It's a pity we didn't get to see what Harry would see if he looked into the mirror. I half-expected to see the scene where Harry looks into the mirror and sees himself transcend his humanity, becoming an immortal intelligence running on a Matryoska brain, then uses his newfound god-like powers and cognitive abilities to take Hermione's body apart atom by atom and reconstruct her back as a living Hermione, helps her ascend as well, so that the two of them can defeat death, optimize the world, and go on doing all those awesome things Harry once said he wanted to do with immortality ...and then Harry looks down and sees that he has a nano-factory in his pocket that can help him start this transition.

I mean, while EY told us that Harry would not build an FAI, he did not say "Harry will not become an immensely-powerful FAI"

This whole trail of thought also reminded me of what a certain Milo Amastacia-Liadon from a certain other HP fanfic saw in the mirror. We all know that Rational Harry doesn't aim low, does he?