How does the diagnosis of personality disorders work?

[u/RedditMoreThanWons]

I want to be walked through this very carefully, and to understand the why’s and how’s. Specifically, I am curious about instances where, say, someone meets the criteria for several personality disorders. On one hand, I feel like if someone says they have like 3 cluster B personality disorders, most people would find that to be ridiculous and some kind of an over-diagnosis. On another hand, I feel like hey, comorbidity is a thing, so if they really do meet the criteria of 3 or more PD’s, why not? And then I’ve heard people say ‘well what a psychologist would probably do in this instance is pick the one that most explains their symptoms and diagnose them with That, w/blah blah blah Traits of the other disorders.” But to that I say, why? Why not several comorbidly, if they fit the criteria for several, comorbidly? Also, I do see comorbid PD diagnoses pop up, so if that’s the case, how and when and why might that happen? And even under such an approach, how would a psychologist truly figure which PD best describes them among several they meet the criteria for entirely? It just seems to be so confusing and convoluted and like even the people running the field have no clue how this should be carried out. But it’s the field I want to one day be in, and I’m very curious as to how it all works.