One of the things I find most fascinating about personality is that you will never find any set of identical people. Common traits, sure. Matching upbringing, yeah. Similar behaviors, of course. But you will never find 2 people who are exactly the same all the time. Our personalities are malleable and always adapting to the fit in with others around us, but never quite losing what they were before. Our Identity is a complex history of everyone we've ever come across and everything we've ever done.

And we should expect identity branching from individual to individual; even identical twins who may be practically the same can not occupy the same space at the same time, so there must be some divergence. But branching within an individual...How does that happen?

When it comes to analogies cognitive psychology and computer are no strangers: Perhaps its similar to dual-booting, virtualization, or just a multi-user system. If that human brain is capable of running multiple persons it may be subject to the same limits of resource sharing and allocation or just have ACLs which would explain branching.

We don't understand DID, MPD, or whatever we want to call it. It's unusual and there's no reason to believe our brains should develop in such a way. Not to sound de-humanizing but it needs to be studied, just like "normal" personalities need to be studied.

If people can live comfortable, healthy lives with multiple identities than I hope we can come to accept it, and sooner rather than later. But we also have to consider how it affects other people, for example another VICE article was posted to HN a while bask describing their perspective while a partner had a dissociative episode: https://news.ycombinator.com/item?id=9144552