It is true.
Years ago, when I was recovering from a relationship with such, wkpedia listed about 9 or 10 bullet points to be a full-blown NPD, and they are remarkably similar to the leftist mindset! That's why I pulled Reeses in...not sure if you were tongue in cheek there, if so, it's truer than you think!
I've not heard of the 'laughing no' test, could you steer me toward more info?
PS - read my profile, I think you'll enjoy it.
I tend to believe leftists to be closer to the BP and sociopath, but, as you stated they’re in the same family of disorders
One quick example...
Watch “The Fastest, Easiest Test For Narcissism -— Up to date: “The Smiling No Test”
https://youtu.be/vcWvJmWIlo0
There are better ones out there, but this is GOOD intro.
Essentially it is rejecting the NP scheme while laughing at the absurdity.
Real life example EVERY guy in a bar has seen...
“Hey dude, but me a drink”
Reply while laughing; “um, no...you should be buying me drinks in exchange for the chance to meet this great guy”
Normal reply is to laugh along
NP will rage that you’re an a-hole.
The inappropriate anger is the key insight.
To the NP your rejection with laughter reaffirmed their self hate. They internalized the rejection instead of seeing it as humor. Their brokenness is THE single thing that drives their actions and views of themselves in the world.