As someone who loves J (though I'm far from mastering it), I certainly wouldn't want to work with it either. J (and APL) really shines when you're playing with

As someone who loves J (though I'm far from mastering it), I certainly wouldn't want to work with it either. J (and APL) really shines when you're playing with it in interactive mode, gradually building sentences and looking at the output at every step. In my case, I've been using it to experiment in algorithmic composition, and I find it forces me to think in interesting and potentially powerful ways. But, as you say, browsing through a large codebase in J would be not be a fun experience. The only way to handle it for me would be to comment it heavily and keep each line as short as possible (which is indeed what maintainable J files tend to look like). So I reserve it for experimentation - and I'm finding it very adapted for the purpose.