General Views
What is Multiplicity
I subscribe to the theory of Structural Dissociation to explain what causes a system.
I believe, therefore, that all systems have the same origin-- dissociated parts of the brain, irregardless of trauma status.
If non-traumagenic systems hypothetically exist, the formation of their brains would still match that of a system which had endured trauma, causing alters.
On Self-Diagnosis
I am self-dx friendly. I recognize that not everyone has the resources to be diagnosed, and in some cases it may take upward of 6-9 years to narrow down a diagnosis.
Professionals are often hesitant to label clients with something so "rare," vetting out other possible explanations first and may lean toward a belief that it isn't a real thing.
But it shouldn't be something you self label with to appear mystifying and unique, be cool, or for fun. Self labeling as "plural" for these incentives is also unacceptable for reasons I'll explain.
What Science Says
I am not a hard prescriptivist to science and treat it like dogma. I've seen science be wrong. I've seen it be incomplete. But, I think there are things we shouldn't ignore about what we do know:
For instance, that systems typically occurs within the developmental stages of adolescence (often before age 9), that it physically affects the brain, and has a disproportionate correlation to trauma.
To conflate these realities with spiritualism (tulpas, soulbonds from other dimensions), freewill (creating "headmates" for recreation) and fantasy (fictional kins) is to be negligent and obfuscate factual information from those who are struggling to comprehend and navigate them.
How I See It
I understand multiplicity as being a neurodivergency akin to autism or ADHD to which, the exact causes of formation are also unknown.
From this perspective, it's possible structural dissociation could occur "on its own" without needing be expedited by a dire cause such as "a specific incident of severe trauma i.e abuse.
However, I do believe some passive environmental stressor(s) need be present for the brain to adapt in such a way regardless if one would label it trauma.
Despite whatever the truth may be, more support and tolerance rather than fear and stigma are needed and could lessen the burden of our existences.