oldgit: Quite right, your last paragraph is a great summary of this.

Agreeing with Dr Silverstone, there was a recent letter to the NYT in which Allen Frances, who helped write the definition of Narcissistic Personality Disorder, asked people to stop saying Trump has it. His point was that being a "world-class narcissist" does not equate to having NPD, and applying the label to Trump does a disservice to the mentally ill.

A point that he made is that NPD sufferers experience "severe distress and impairment", which is not evident in Trump. Rather, Trump seems more able to cause severe distress in others.