Emacs-specific solution, but there is this[0] example of J and prettify-symbols-mode, the results look something like this:

    quicksort=: (($:@(<#[) , (=#[) , $:@(>#[)) ({~ ?@#)) ^: (1<#)

    quicksort ⤆ ((∇⍛(<#⊣) , (=#⊣) , ∇⍛(>#⊢)) ({⍨ ?⍛#))⍣(1<#)

[0]: https://wjmn.github.io/posts/j-can-look-like-apl/