Hi all - there's interesting discussion. I'm not on the NPD spectrum, but am on the flip side of the coin as a (recovering) co-dependent. Just like Echo and Narcissus, the narcissists from my past and myself fit together perfectly.
As a non N, and relationship and friendship partner of many folks on the NPD spectrum, I can offer a slightly different point of view that hopefully is helpful?
Speaking from my experience and learnings/professional help, ladies and gentlemen can lie anywhere along a wide spectrum. We all have some narcissitic tendencies of course. Some folks have a kind of "healthy" narcissism, some might be further along with a bit of "unhealthy" narcissism which doesn't mean that they necessarily affect anyone else besides themselves or sometimes they do, some folks display a large spectrum of BPD symptoms, some folks would call themselves a narcissist or BPD demonstrating the symptoms described in the most current DSM, some may be further along and lean towards malignant and/or sadistic narcissism and then others go all the way toward the sociopath side.
Some folks affect others and may use them, and some do not. Some function on a higher level and some on a lower level. Some are more aware of themselves and some have buried things very very deeply and may not always be consciously aware. Some are covert and some are overt. Some are quiet and some are bubbly and charismatic. Some hurt others on purpose which gives them enjoyment and others do not at all. Some people may misuse or overuse the term as well. There's just such a diversity, and it's even more complex because we're all individuals and cannot simply be pigeon holed and categorized so simply.
My experiences have led me to believe that in no way does narcissist/NPD=bad or evil person. I have never observed an automatic correlation, and I do believe the name unduly gets a bad rap from the get-go. Just as we all suffer with our own maladies, so do the NPD folks, from my experiences. Kind of like a coping mechanism because of difficulties from their family of origin or perhaps some trauma or abuse. I feel closely related in that sense as a co-dependent who went through the same thing but adopted a different unhealthy coping mechanism....
I suspect, as always, wether someone has an identified mental illness or not, if they are harming you or others in any way, you must take care of yourself and those in need of your help first. That's really not something that only applies with NPD folks because not everyone hurts others, and other mental illnesses and folks without an identified mental illness can do the same. Therefore, in my experience, that's not a clear identifier of a narcissist.
The folks I was with who ended up being the most severe and malignant narcissists were often covert and very hard to identify, especially for folks without prior experience. They can wear many masks and they can have tricks up their sleeves that you might never have imagined. Many stories and articles are written about people who were married to a narcissist or have narcissistic family members or friends that they didn't come to understand for years, sometimes decades. Some folks I know who are on the spectrum are nothing like that, with dark whitty senses of humour and won't hesitate to set you in your place. lol
The only thing that I can honestly say about helping someone identify folks with NPD if they don't tell you themselves or maybe don't know it themselves, is simply - your gut feel. The false self is presented. Especially if you're a sensitive-type person, you listen to yourself and pay attention to your deep inner feelings, and it's amazing how many times it's right. Something might not feel quite right, maybe a little twitchy feeling, something might feel just a little out of place, might feel like a piece of the puzzle is missing, something might just irk you or nag a wee bit at the back of your brain - if that makes any sense!?! Lol This may or may not happen immediately, but always seems to happen as more and more time passes. I'm sure folks will often tell people to listen to their guts anyways, so it's best to do anyways in all situations.
Hopefully that's helpful in some form for folks? I myself am always learning more and more about myself and my community around me, so take my experiences with a grain of salt.