I don't use Lisp but this is very readable to me, actually way more than the examples in the article by a lot. I actually understand this code, just because of how it's formatted. Maybe I'd just use 2 spaces instead of 4 but otherwise, looks good.

Granted I'm not the one to optimize for since I don't use Lisp, but this just seems sane and easy to automate, and it looks like other non-Lisp languages.