Okay, so my take on your question is: the universe is too full of information and relationships for us to understand, to represent in our minds. So we know something when we learn to take some links into consideration and ignore all the rest.Knowing and defining is not so much about taking in, but about leaving out. With this in mind, thinking about a person is necessarily reductionistic, because you are building "a mental wall" around some phenomena to think of them as separate from others and become super-aware of what they have in common. It´s all a mental trick, it´s not realistic. But it is very convenient, because it allows us to focus our energy, to guide our behaviour. A person is really in my view, the symbolic avatar that our tens of trillions of cells, bacteria, protozoids etc use to communicate with other pluricellular colonies with similar interests, that have their own personae ("masks") or avatars to chat with our avatar. A person is an entity of the level of reality, or complexity, that is also inhabitated by dogs or blackbirds or vacuum cleaners; but not by bacteria or the Moon. The Moon communicates with entities in her level in their particular way, basically through gravity and radiation. Bacteria communicate with other bacteria with their chemical and electrical signs. Personae themselves are symbolical creatures (they are avatars or images) so they communicate with each other using symbols and meanings. Our personal or symbolic or "spiritual" self, is an ongoing update on past records of the states the colony have been going through so far; not direct medical and physical descriptions, but the symbolic or poetic record that was made for the persona files.
The purpose of the avatar is to deal with the macrocosmos level of the cellular system in a way that is conducive to the survival of the colony and the survival of other similar colonies. If the avatar had not other avatars to communicate and work with, it would lose its purpose; that is why lonely ladies adopt cats and why saints in the desert had so many imaginary friends. If you upload your mind into a computer before you die, your persona or soul dies with the body anyway, and the upload is just a record of the last state of the symbolic function of that poor body. It can be used to make a digital creature, that I guess will seek desperately for a body to be attached to, so as to avoid extinction or dilution. But it´s not you, so you don´t need to care about that program and its troubles.

Maybe one way to look at it is to consider how different psychologies are developed in specific schemes of causality and views of environment that place what develops through description in a context. That may be reductive or not, depending on the "world" assumed to be where certain properties are expressed.

Take Erik Erikson, for example. As a matter of modern parlance, he coined many of the ways "identities" are said to form. In that sense, he is more structuralist than the Freuds or Jung whose forms and descriptions of dynamics were more focused on what drove or energized a system. What having an "identity" means in each of those systems is more of a result than a perceived property.

At the other end of scale, the Skinner form of behaviorism does not include any of those expressions as being a description of what is happening. Strictly speaking, that endeavor is not a reduction of other meaning but a circumvention of them. Like taking a circle highway in a city to avoid all the intersections.

Another element outside of the science game is to see how personality is observed. A description by Flaubert, La Rochefoucauld, or Kierkegaard may brush by the same quality but you, the observer, would have to be the one who saw it in a certain moment of discovery.

I understand this argument and I don't bother addressing it intentionally. There is essentially a lot to consider. But my philosophy is intentionally convenient because it's the same logic that most people use. Even you I would argue might be having a hard time separating this traditional view point from your own. This is more of a counter argument to the traditional concept of identity than it is an argument between scholars (something I forgot to mention sry).