I have no assumptions about schizophrenia, I just paraphrased how the definitions of the ICD-10 work. The fact of suffering is the distinction between a mental disorder and a quirky personality.

Think of it as a continuous spectrum from the idealized normal person (the center of a bell curve) to the person having significant problems living a normal, fulfilling life. The eccentric personality is somewhere in between.

This is all about definitions. The ICD-10 and similar categorizations essentially work by listing a number of symptons and a minimum count of symptoms a patient has to have to be diagnosed according to this definition. They don't make any assumptions about disorders existing per se.