Some shaders author are really good at commenting their code. Shane for example. And top quality shaders on top of that https://www.shadertoy.com/user/Shane
There are countless insanely talented creators at ShaderToy. Shane, IQ and FabriceNeyret for example. I try to learn from their code as much as I can, but I still don't even scratch the surface of their talent. Those guys creations are an inspiration, and I can only hope to learn a fraction of everything they share with the community.