^^I interpret this as the definition of a narcissist.
IMO, a 'high-functioning BPD' is actually a narcissist.
IMO, by definition, BPD is a low-functioning condition. It is exemplified by self-sabotage, self-destruction, and lack of ego.
As I quoted and tried to describe (other very experienced members are able to describe it far better), the term was introduced due to the spectrum of the disorder in order to broaden accessibility/readability for people.
The psychologist Theodore Millon (expert on personality disorders) even proposed subtypes, so :
Discourage
Petulant
Impulsive
Self-destructive
For me the above mentioned subtypes are not that “accessible”
Low Functioning, from the living train wrack BPD that find great difficulty to coop with daily life (who have an impact of a 10% of the psychiatric services! = A. Skodol / J.G. Gunderson, The Borderline Diagnosis 1= ) up to opposite HF, the ones can manage their lives, be productive and generally keep their relationships “civil” and appear to be normal driven people one moment then “moody”, inconsistent and manipulative the next.
Please do not forget the very basis of the disorder: attachment, the fear of abandonment
So, yes, from that perspective there is no High or Low Functioning as the core from whom a pwBPD operates is the same.
As we on this Board are armchair psychologists (except for a few professional and/or highly educated members) and in fact trying to explain events from our experiences, IMO we must be aware not to over generalize and label easily certain behaviour and/or link it with disorders that has a different origin but is “used” by a pwBPD.
True, the highest percentages of comorbid disorders are: NPD, Mood disorder (bipolar), Anxiety disorder, PSTD, Substance abuse and Eating disorder.
As you mentioned the disorder of narcissism. The core (the reason) from which a narcissist (grandiosity) act is different from a BPD (attachment / abandonment).
A sociopath, as mentioned earlier in this topic, does not act from the same core as a BPD. Short: a sociopath does not care for love, nor feels remorse. In contrast a pwBPD, who crave for love, feels deep shame, however can’t process it as we.