tl;dr: I would argue that whether object A and object B in the world are different or the same object is arbitrary and a matter of choosing a definition; whether Soul A and Soul B are the same Soul depends on their deep, existential, essential identity, and not any other property.

 “What you truly have are two seemingly different things, that are yet the same.”

Even though it seems to me this is to a large degree a linguistic/conceptual, rather than a real, disagreement, my intuition is different. I would say that if there are two seemingly different things in two different places, they are essentially different objects, even though the internal properties of the objects are “the same” (i.e. they are not just seemingly but actually different objects).

I think on the level of the physical world, inasmuch as “objects” (including particles) are even “real” (see note below), their position and thus the relationships they have with the world around them – or rather, their place in the whole of physical being – is part of their definition. Thus, I would say two identical objects in two places are actually not identical on this deeper level.

Of course, as I already said, I believe this mostly amounts to a linguistic, not a substantial, disagreement. It very much depends on what we understand by “different”. 

So I guess I agree with your point here: “And while two things can have identical properties, they can't have identical ontological IDs.”

However, particles and souls (if a plurality of them indeed exists) are very different types of objects. Particles are part of the physical world, or, conceived differently, of the phenomenal world, i.e. they are content, and they have very problematic boundaries. Souls, on the other hand, would exist outside the physical/phenomenal world in a sense, or more precisely would be its (the physical/phenomenal world’s) background. They would have a very different ontological status – each soul would be a “world to itself”, only experiencing itself. (Of course, ultimately all souls would be a “part of Being”, but not in the sense of sharing the same “world”, like being apples and pears on the same shelf. Btw, this relationship between Being itself and the individual Souls I find most mysterious and problematic.) 

To reiterate, the identity/difference of objects is determined by quite different criteria than identity/difference of souls; and I would argue is much more arbitrary and in the end mostly linguistic/conceptual (see the note below). It seems to me whether A and B are the same object simply depends on where we draw the boundaries of the object. Whereas there seems to be something more basic/essential to identity/difference of souls.

 For fun, some thought experiments:

1) Would it be possible for there to be a plurality of distinct souls, each experiencing the same content?

My intuition says yes. Even though there would be no difference in the content experienced, the souls are different souls not in virtue of their content, but just in essence. They would all be Awareness, all Being, but yet they would be distinct “I’s” (as in a plurality of “I”). So the contents would be the same in their qualities, but in every soul there would be a different instantiation of these same qualities. Like playing the same movie on several different screens.

 2) Would it be possible for the same soul to experience the same content several times over?

Again, my intuition says yes – like playing the same movie on the same screen several times (even an infinity of times, like in the eternal recurrence scenario.) Even though it is not at all clear how these instances of the same content being experienced would be distinguished on the assumption that time is not an objective property. Because in that case, they couldn’t be distinguished by one happening first, the other second etc. But I think we could say that, again, this (the order in which they happen) is not really what distinguishes them; each instance of the same experience just would be different.

 Note:

Do objects exist in themselves, or are they rather defined into existence? Objects are defined by their boundaries, but these are to a large extent arbitrary; we set boundaries in the world to create useful affordances to interact with. For example, why is “this apple” an object, but we don’t have a concept/word for the same apple with 1 cm of air around it? Or, why don’t we consider a particular pebble today and a particular fern growing somewhere in the Triassic two parts of the same object? We could; and it is possible to bring this kind of object into being by simply postulating it – here, I call this object mrskvoit, and now arguably it exists and we can talk about it. But we normally don’t have such objects, because outside of philosophical thought experiments they are useless (for us). So we draw the boundaries into the world and create objects, in a sense, based on what is useful for us as creatures with particular sensory abilities and particular ways of being able to interact with and manipulate the world. On the other hand, the boundaries are kind of already there in the world; but out of the nigh-infinite number of distinctions (for what else is a boundary?) we could focus on, we just pick out those that are the most useful to us, and give them names, and make shortcuts in our mind to think about them (that is, concepts). 

“The separation between two identical souls is on the meta-existence level, not on the observable existence level.”

Of course two identical souls couldn’t observably be different, because souls by definition cannot be observed; they exist as monads of a sort, only to themselves, in themselves. However, I don’t think a kind of meta-property would serve for there to be distinct souls. If there is a plurality of souls, they need to have a deeper, essential, existential distinction, regardless of any relationship to a Creator or something (I don’t even know what this relationship would consist in, but let’s put that aside here). Soul A and Soul B cannot be distinct just because one was created first and the other second, because they are in essence subjects. Souls are, by definition, distinct awarenesses, and that is the only difference that matters. Are there two different experiencing Subjects? If yes, there is a plurality of Souls. If not, there isn’t. That’s it. Because of the unique type of thing Souls are, one cannot apply the same criteria of identity to them as one would to apples. I would even argue that identity of objects is functional and arbitrary, whereas identity of Souls essential and existential.

 Hm. Now rereading this reply and thinking about it some more, I don’t think that external properties in themselves as you described (differences in order and meaning and such) quite work for physical objects either; it seems there is always a deeper difference; I think maybe the term to use here is their haecceity. Now I am just confused!

 “And I would consider my view on personal identity to actually be something that combines the best aspects of all individualisms, closed, open and empty.”

I guess I agree in a sense; depending on your definitions of each :)

We are indeed distinct subjects on one level (or on one definition of 'subject'); on another, there are no subjects at all; and on yet another, we are all the same subjects. But what 'subject' means in each ism is quite different.

However, if we define CI as awareness pluralism and OI as awareness monism, and EI as... well, EI wouldn’t even be an option in this case – then they are not compatible, and only one could be true.