> Looking at all the parens of even that simple lisp factorial, and I realize that I'm feeling a lot of cognitive load that would simply never go away, because the punctuation doesn't let me filter any of it out. I'd have to read everything more carefully.

Completely the opposite here.

Parens means function call or list. Lists usually denoted by a quote first.

I don't read the parens, I skim everything, reading words. And the punctuation is really simple.

For example:

    if (number? a)
      + a b
      error "Not A Number" a

I stripped most of the parens there, (like Wisp [0] does), because I don't really see them. I see function call and arguments, because there isn't anything else.

Scheme has the very least syntax out of just about any programming language I've used. It has a tiny cognitive load compared to most.

[0] http://dustycloud.org/blog/wisp-lisp-alternative/