Yeah, its pervasive use of explicitly, deliberately nonhygienic macros was surprising when I first read it. Interesting to consider and also good to understand why it'd be a nightmare to debug code written that way.

There is plumbing code and there is porcelain code. There is nothing wrong with being clever in the plumbing area, even with other people peeking under the hood. The porcelain side is more nuanced though - it takes a special kind of cleverness to deliver intent with clarity.

A personal anecdote - not long ago I saw a beautiful piece of code (not mine) using the Result monad being rewritten as a chain of nested if statements - all because it was "too clever to understand". Go figure.