To start it’s important to understand what identity isn’t: Identity is not a password, it’s not root access, it’s not your calendar, it’s not your email, it’s not a technical achievement, it’s not your location, it’s not a user account in a system, it’s not your contacts and it’s not a feature.
So, what is identity? I think in its most basic form, your identity is the product of how you manage your attention and others’ access to that attention. Those areas where your attention is focused assemble to form a set of experiences that shape and influence where you’ll direct future attention. But that attention is interrupted all the time by people, events, things, desires, boredom, weather, etc. and that process of interruption is, largely, contained to physical space because that is a natural gate on access.
Where does the identifiable part of an identity reside? Maybe it’s related to the nesting dolls you’ve mentioned and this “sheathing effect.” Returning to Stuart Brand, he describes the identity of a building along similar lines with his notion of “shearing layers.” Brand notes that just as people grow and change, buildings grow and change—they are not static or fixed.