because so much of the meaning of anything we say depends on context and affect, narcissists (lacking empathy and thus lacking both context and affect) hear only the words.
I think this is getting close to the heart of the issue. I am not sure that Ns lack affect though, I think they are stuffed full of it. The trouble is, they have so much of their own, that there is no room for anyone else's.
I am half N/psychopath because I have blunted affect. I deal with this (as far as it is possible to do so) by acting 'as if' (because I was not always like this, and I remember). But it means that I focus on words, and not on the emotional connections, perhaps more than I would like to have to. It is like being a robot sometimes.
I am trying to think of a way to explain what N behaviour with language is like. It feels like someone who stuffs themselves with icecream all day, then goes to a dinner party, feeling rather sick. No matter what is served, no matter how delicious, they are always going to feel rather sick, and not be interested in any food on the table. They will not understand hunger in anyone else at the table, and will pretty well inevitably ruin the evening for everyone. (It is hard to understand hunger when you are stuffed with icecream and feeling nauseous.

)
Any discussion of food is likely to return very quickly to ice cream; fine for them, rather uncomfortable for everyone else.

Anyone sensible would either not go, or else would not overeat first. With the N, they can't help the immediate gratification part, nor can they admit that what they have done is wrong, or that other people might have an alternative perspective.
In effect, they want us either to cancel the dinner party and starve until they are better, or else to sit guiltily picking at our steak and chips, while they regale us with tales of icecream they have known, and how much better it is than anything else.
N affect is so stuffed with their own needs that there is no room for even noticing that anyone else has any needs at all, let alone any that differ from the N.
In terms of language, there is no perception that the variant they have is not the standard one, because the centre of the universe has to contain the standard. Anything else has to be peripheral and therefore subordinate. So if we all say 'bottle' and they say 'pipe', we are the ones who are wrong.
As has been said, if anyone stops a conversation and starts to demand definitions of other people, communication is pretty well always going to break down. It is a smokescreen, to deflect attention away from whatever subject it was getting close to.
So, is communication ever possible with an N? Probably not, unless we are talking about them and their needs and wishes.
But we still don't quite give up trying ...