I am traumogenic (trauma created/clinical DID) plural system. It is highly likely that I never had a "core personality" that I was born as and instead have always had either an infant mental state or multiple personalities. (During the time most babies begin to form a coherent personality, I formed several. It is possible that not every system forms like this but highly like I did)
Every time I've felt I was singular, I've experienced mental walls, amnesia and other DID symptoms. If someone could do a "I'm singular ama" that'd be cool because I have questions too. :)
Various forms of voice hearing is way more common than people talk about but there is a lot of stigma. People who have schizophrenia actually have better treatment outcomes in "the third world" than in the "first world" (generalization) because often times those societies accept that voice hearing is a part of the human experience for many people as opposed to something shameful or wrong