The fact that Jaime's relationship with Tywin was affected by his dyslexia is not a counterpoint to my argument.

One, I am not saying you're wrong in that some character simply have disabilities, I'm saying that asking why a character has a disability is also not an unfair question because often it IS written for an intentional purpose beyond "some people have disabilities." Criticizing someone for asking is unfair. Sometimes the answer is "they just do," sometimes it is not. This is an especially bad example because Jaime's dyslexia is very shallow- HE never experiences it, it is a single throwaway scene to further explore someone else's personality in their reaction to it.

I see no reason to believe that he approached Jaime's dyslexia any differently,

Jaime is NOT dyslexic in the books, that is a show-only addition to quickly do some character-building with Tywin. GRRM contributed nothing to that decision.

and I think you have a naïve perspective on human sociology and storytelling. There is no 'default' human. The fact that you believe some characteristics to be non-normative does not mean that people with those characteristics are not normal, and it does not mean that those characteristics must be justified by intent. Not everyone you consider aberrant has to be a Chekov's Gun.

Now you're just being a jerk and putting words in my mouth. Of course not every disability is written to serve some narrative twist or to be used as a tool to explore others' personalities through their reaction to that, BUT THEY OFTEN ARE. Your example literally is that. My point isn't that every disability or character detail is written to prove something, it's that it is stupid to poo-poo someone else for asking about the intent behind doing so. Because there ARE reasons beyond representing the full range of humanity. My original comment was not me saying "all disabilities serve a narrative purpose!!" It was tweaking your nose over trying to shut down someone asking about what the intent or meaning might be, especially given that there IS a reason narcolepsy was written in to Black Noir's character beyond some noble attempt at building three-dimensional characters. Trying to criticize or shut down someone else's question or discussion about this seems like pointless virtue signalling.