I was talking about cluster B disorders in general, and not BPD in particular. A lot of the literature I've read seems to indicate that BPD in particular can be an unhealthy coping mechanism for extended childhood trauma, which also explains a lot of the comorbidity. But a high-functioning narcissist or antisocial or even borderline who doesn't have any other untreated disorders might be completely toxic to everyone else in their lives without ever suffering any consequences themselves, as long as they can cycle through victims and enablers fast enough.