Shouldn't there be some definite fact of the matter as to when one person becomes two people?

And even after you know that the falling tree creates acoustic vibrations but not auditory experience, it feels like there's a leftover question.

Did the same Eliezer really write both of these statements? I say again: if you can have all the information about an Ebborean brain split, but you're still asking 'when does one mind become two?' then you've missed the point.

A conscious mind is not a single, indivisible entity. It is a slippery thingy arising from the interplay of myriad smaller systems and mechanisms. If you want to use the word 'emergent' then knock yourself out. With that in mind, why should there be a definite fact of the matter?