My point is that genius is exactly not that. Code like in these examples is, to my mind, a tour de force, only interesting as a curiosity, or an example of a terrible but clever hack.

(Like you, I of course immediately thought about the famous Artur Whitney's page of impenetrable C.)

The genius of J (and APL) is exactly in the simplicity of the language, where a single character denotes a whole well-defined operation on arrays which might take a page of Fortran code, and these operations are orthogonal, and useful for practical purposes.

But to some people apl/j are horrible, they will prefer their spaghetti of routines massaging random dicts where everything is "obvious"