Docs: tone and style pass

[Technologicat]

Standing documentation tone/style items:

• Check the tone of our criticisms of Python — for the most part, the language is excellent (if it wasn't, this library wouldn't make sense). Worth mentioning what Python gets right: focus on readability, vertical-space-saving indentation-sensitive syntax, the general with protocol.
• Consider switching from Title Case in Documentation Headings to Just capitalize the first word to increase readability. It's a feature of capital letters to catch the eye and stop scanning — let's use that effectively.