What's interesting is that in reference [1] you provided Iverson himself reveals exactly what I said about the reasons for which J abandoned APL's symbology. Here's an excerpt:

"When we came to implement APL, the alphabet then widely available on computers was extremely limited, and we decided to exploit a feature of our company’s Selectric* typewriter, whose changeable typing element allowed us to design our own alphabet of 88 characters. By limiting the English alphabet to one case (majuscules), and by using the backspace key to produce composite characters, we were able to design a spelling scheme that used only one-character words for primitives.

Moreover, the spelling scheme was quite mnemonic in an international sense, relying on the appearance of the symbols rather than on names of the functions in any national language. Thus the phrase k↑x takes k elements from x , and ↓ denotes drop.

Because the use of the APL alphabet was relatively limited, it was not included in the standard ASCII alphabet now widely adopted. As a consequence, it was not available on most printers, and the printing and publication of APL material became onerous. Nevertheless, in spite of some experiments with “reserved words” in the manner of other programming languages, the original APL alphabet has remained the standard for APL systems."

I actually had one of those IBM Selectric printers with a custom APL print head.

The thinking behind this approach was completely flawed. APL wasn't and never did compete with BASIC or FORTRAN. It was a language ahead of it's time and one that used symbols associated with meaning much like math does. The integral symbol is understood by US, Russian, French and Pakistani scientists and engineers without necessarily having to know each other's spoken languages. That's part of the power of notation as a tool of thought, ideas are reduced to these symbols that are filled with meaning. For example, ⌊ and ⌈ represent minimum and maximum, respectively. You only have to see these once to get it and, likely, never for get it.

Why is notation a tool for though? Well, the paper I referenced in my prior post covers this well so I won't try to redefine it here. Using the example of the symbols I introduced for minimum and maximum we can show a simple case of this:

A ← B ⌊ C

Means "set A to the lesser of B and C". Which would be something like this:

if(B < C)
{
A = B;
}
else
{
A = C;
}

Or

A = (B < C) ? B : C;

The latter feeling more "expressive" and concise.

So, what's the big deal, the second form (or a range of other forms) are easy to read and understand. And that's true. Yet that isn't notation, it's a bunch of ASCII text and unnecessary stuff that ONE SYMBOL can replace.

What happens if A, B and C are arrays of 100 elements? Or, matrices of 10 by 10 elements? Or tensors having 10 by 10 by 50 elements?

Well, in APL the expression might still be relevant:

A ← B ⌊ C

This will result in A containing the result of comparing B and C element by element and picking the smallest of the two. Now we are expressing ideas without piles of code. A C-like language would require two or more nested loops, indices, etc. Your mind quickly starts to separate from living in the problem space to dealing with the mechanics of expressing ideas. A single symbol becomes ten lines of code.

BTW, I said "might still be relevant" because it depends on what we are after if we are comparing two vectors for a "minimum of B and C" condition. I won't get into all the permutations. I'll just keep it to the simple case of an element-by-element comparison.

When we introduce the scan operator "/" things get more interesting. This operator applies the function to the elements of a vector (or the first dimension of a multidimensional array):

A ← ⌊/ B

This will take array B and return the smallest value. If B is a matrix, it will do this for each row.

Again, we are expressing ideas with simple symbols, just as we do in math.

J departed from this in order to solve the weird symbols "problem", when in reality, the weird symbols were what wielded APL's power and, in my opinion, could have become the future of humans telling computers what we want them to do and how.

Think about it. Why do we need so many ASCII-english-based languages? A loop is a loop is a loop. A conditional is a conditional is a conditional. Objects, classes, functions, etc. Same crap. And, in most cases, in the end, very similar machine code.

We need to eventually make a departure from this and create a "CS language", one where doing something like finding the smallest element of an array boils down to a symbol and not much more than that. One where, perhaps, a genetic binary solver or just the genetic step of mating individuals of a population can be represented by a single symbol or a set of relevant symbols. Perhaps sorting can have it's own symbology.

I'm just riffing here but I hope you get the point. Over time CS will no longer be about developing more and more languages that repeat 95% of what every other language has done and will ever do but rather evolve into adding to the symbolic alphabet of CS, which, when executed by any machine, will produce the same results, today or in 500 years, just like mathematics.