Cool! The Moinoid instance for functions was news to me. Comparing on multiple criteria like this is a common enough pattern that I consider using Ordering's Monoid instance a best practice. Nested case expressions creates a lot of noise.

Shlemiel the painter's algorithm :(

http://www.joelonsoftware.com/articles/fog0000000319.html

Yes! Someone else on this website apparently learned that total orderings form a monoid!

I agree. It seems to make more sense because the empty string "" does have (0 pairs of) balanced parens.