Trying to communicate about @[d; i; f; y] works once you know what that does. Like with any mathematical notation, it's given a name just like '+' has a name (plus).
I don't know if it's "inherently" superior (everything is subjective preference), but @[d;i;f;y] seems more amenable to algebraic manipulation. Also, just the fact that it is a function that takes four arguments vs some property of d means along with k's projections (similar to currying in functional languages) you can leave any of the 4 arguments empty to create a curried function.
For example you could do something like @[d;;:;x]'(a; b) which will replace the items at indices a and b with x. Or any number of other possibilities. Compare to python where to cover all possible behaviour you'll need various lambdas + for + zip + map + ...
So that to me seems separate from the minimalist syntax. The problem isn't the flexibility, but the sheer combined density. The problem isn't even necessarily the odd extra operator, but that there are so many of them that are heavily overloaded/
I don't think the projections example is possible to reproduce in an ergonomic way in e.g. Ruby or Python, but you could certainly imagine a syntax extension to allow something similar. Since a closure in Ruby is just another object, capturing arguments and returning a modified closure is trivial, but the syntax won't allow leaving out arbitrary unnamed parameters, and so you'd need an ugly placeholder value; amending the syntax to allow e.g. "f(x,,z)" with an omitted value in between set to some placeholder object wouldn't break anything, and might well be useful. There are certainly parts like that in k that seems valuable.
The dot-syntax vs. a more functional syntax I think is purely subjective - all of us understand both, I just happen to prefer an OO syntax. d.amend(i, f, y) or amend(d, i, f, y) isn't what'd break us. Not the "@" either if it was one of a smaller number...
There aren't really that many, not when you compare it to the total number of python/ruby functions that would be roughly equivalent. (Ignoring the fact a lot of k functions operate by default on matrices and other nested structures in ways that python/ruby/etc can't really do at all)
Yes, it's dense, but that's by design. And in a vacuum it may seem like replacing @ with amend wouldn't have much of a difference, which is true. But replacing every character with the same word (which is tricky - because it's hard to precisely define things, and some characters have multiple meanings) would end up with a line of k turning into a page of prose, losing the mathematical nature of it in the first place.
I don't know if it's "inherently" superior (everything is subjective preference), but @[d;i;f;y] seems more amenable to algebraic manipulation. Also, just the fact that it is a function that takes four arguments vs some property of d means along with k's projections (similar to currying in functional languages) you can leave any of the 4 arguments empty to create a curried function.
For example you could do something like @[d;;:;x]'(a; b) which will replace the items at indices a and b with x. Or any number of other possibilities. Compare to python where to cover all possible behaviour you'll need various lambdas + for + zip + map + ...