What is your particular understanding of “dissociation”, as in the specific signs and symptoms you see in your friend?

No one serious disagrees about the literal existence of dissociative behaviors (i.e. “checking out” for reasons both physiological and psychological), but plenty of people disagree about the phenomenology + clinical nature of DID and related DSM constructs.

Well, I think the issue is one of scale and semantics.

Your post asked about the subject matter in a broad sense, using the keyword "rare".

My comment was based on that, and I gotta say that your response here actually makes my comment more relevant, not less. What you're describing isn't a rarity, it's a small sample group. You can't call something rare in a colloquial context and only point to a local experience, with limited numbers of examples. Well, you can, but you gotta expect responses to include broader perspectives.

The sample group you used is tiny. It doesn't reflect standards of care, or the general professions of psychology and psychiatry.

I would also say that, without seeing the records of the patient in question, your opinion (and mine) of the validity of the diagnoses given is pointless. We don't know if those practitioners do or don't believe in dissociative disorders, only that they didn't diagnose it in this case.

Secondary to that, neither you or I are qualified to make a diagnosis at all, much less based solely on what you've observed of the patient. You say you've observed memory loss, blackouts, and that the patient is still mobile and speaking during the events. That isn't definitive of dissociative disorders. It is a symptom of multiple possible issues, and most of those have to be ruled out as much as anything being ruled in.

In a different comment, you listed a handful of diagnoses, which can present with the same kind of blackouts. Won't always, but neither do the various dissociative disorders.

Now, I will also say that patients in general, and women in specific get dismissed way more commonly than is acceptable. It could well be that that's leading to a misdiagnosis, if that's what this is. I've dealt with that for myself, for loved ones, and as an advocate for my own patients back in the day.

Dissociative disorders absolutely exist, btw. Whether or not they should be called that based on what happens internally is worth some debate. It's also worth debating what the criteria for diagnosis of them should be, if the underlying causation is not what could be called dissociation. The dissociation could well be a symptom of something else rather than a disorder of its own, and thus need to be called something else. It could be closer to panic disorder rather than something like schizophrenia, in other words.

For that purpose, schizophrenia is the diagnosis or the underlying function of the brain. Panic disorder is a maladaptation caused by other things, rather than the actual cause of the panic attacks a person has.

What was the argument for prof #2?

Also, a lot of doctors don't follow up on any symptoms they don't directly witness or have tests for.

Just bad doctors. I've met many whose careers are based on treating these disorders (or symptom of a disorder)