PS linehan thinks that 'borderline personality' would be best construed as a disorder of 'emotion regulation'. i think she is on the ball with that, but don't really see that a change in nomenclature (name) would do a great deal...

the 'halfway between crazy and not crazy' idea comes from this idea: 'on the borderline between neurotic and psychotic'. it is fairly deeply entrenched in psychoanalytic theory. the psychotic disorders were thought to result from very early developmental problems whereas the neuroses were thought to result from later developmental problems (around 2 or 3 for oedipus complex, i think). people with 'narcissistic disorders' (narcisstic personality, histrionic personality, histeroid personality, borderline personality, anti-social personality etc) were thought to have a developmental problem half-way between those two. so... would regress to a psychotic state under traditional psychoanalysis (like the psychotic people would) even though they appeared as your average (treatable) neurotic when they weren't stressed ( or we might say emotionally dysregulating in the context of a relationship due to their relational trauma).

so... the terms 'psychotic' and 'neurotic' have been taken out of the DSM becaue there wasn't any empirical basis for that distinction (and i don't think there was good inter-rater reliability, in the sense of agreement between clinicians, either. that being said unofficially a fair number of psychiatrists still think in terms of the neurotic/psychotic/borderline distinctions. especially those seeped in psychoanalytic theory...