The Psychopath Code is a fantastic reference for how to deal with toxic people, but Hintjens (as he readily admits) had no knowledge of modern psychology or psychological research and no training in that field aside from self-teaching and "in the wild" experience. His definitions for who a psychopath is and how they behave are thus completely out of sync with how the rest of the world identifies such persons. He does not distinguish, for instance, between different kinds of personality disorders - Narcissistic Personality Disorder, Borderline Personality Disorder, etc. - and psychopathy, even though they are quite distinct. It is not accurate to call the people Hintjens describes "psychopaths," but simply "toxic" or "pathological."

That doesn't mean the Code is not valuable - it is extremely useful. But it is not a good reference for learning about psychopathy in particular.

(Full disclosure: I personally had some brief communication with Pieter Hintjens a few months before his passing, where we discussed precisely this issue in the context of some family members of mine diagnosed by professionals with certain disorders, none of them psychopathy. While the conversation was fascinating, it ended when I suggested that it was valuable to ask not only "what does this person do that harms people?" but also "what motivates them to do this?"; a psychopath does not share motivations with a narcissist or someone with BPD, for instance, and it didn't seem he was willing to accept that distinction.)