Well, there can be a question of what rate of disposition change is consistent with being still the same person. About telling apart - well if someone cannot tell a computer program and animal apart, they have a trouble.

It looks like currently humanity can learn a lot about concept of self but seems to be a bit afraid to try by medically temporarily freezing inter-hemisphere link... What would the person remember as "past self" after re-merging?

All this is moot anyway because gradual uploads are as likely to be possible as stop-and-go ones.