In J, the parens, brackets and braces aren't balanced because those 6 symbols, i.e. `(`, `)`, `[`, `]`, `{` and `}`, are used as standalone symbols for other syntactic stuff, making J code very hard to read.

No, parens are parens, used for grouping. The rest is true, though: brackets `[`, `]` are essentially two flavors of identity function (dyadic) and `{`, `}` are indexing operators (not sure I remember right, but I think `(<1;2) { A` would be `A[1][2]` in more common languages).

Parenthesis are paired and have their usual function of groupoing. You are correct about brackets and braces though. Personally I do think J is often hard to read, but not because of the unbalanced brackets and braces.