It's interesting to see how much Haskell has changed since this was written. It feels weird not having every Monad be an Applicative Functor. (Sidenote, I really like that you can define a Monad instance in Lean 4 and automatically get those. I guess Haskellers derive this stuff anyway, so it's not the biggest deal)
It looks nice, and I'm glad that it's semantic and responsive, but the fundamental problem is that monospace just isn't great for body text. I've read blog posts on multiple sites with monospaced body text, it's okay, but proportional really is the way to go in my opinion.