What makes those diagnoses "neurodivergent" and the others not? Why aren't other diagnoses "neurodivergent" too? How exactly do we define "neurodivergent"? (And why is that the right definition to use?)

> They don’t have much overlap with personality disorders (which do have a lot of overlap among that category).

There is a lot of overlap between the disruptive behaviour disorders (DBDs) – oppositional defiant disorder (ODD) and conduct disorder (CD) – and ADHD; so much so that ADHD is sometimes considered a DBD along with ODD and CD. And there is a clear connection between CD in children and adolescents and ASPD in adults – indeed, a child or adolescent with CD can follow one of two trajectories, either their conduct problems resolve with maturity and they become law-abiding pro-social adults, or else the child/adolescent diagnosis of CD evolves into the adult diagnosis of ASPD. So there is definitely a connection between ASPD and ADHD. A child with ADHD (even without comorbid CD) has an increased risk of developing ASPD as an adult – https://pubmed.ncbi.nlm.nih.gov/24284138/

Some researchers consider ASPD to be a neurodevelopmental disorder – https://pubmed.ncbi.nlm.nih.gov/29401045/ – which is the same category that ASD and ADHD (and sometimes also OCD) are put in.

There is also a lot of overlap between ADHD and BPD (Borderline personality disorder) – https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4739390/

There's also overlap between ASD and BPD – https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5590952/