I love what Robert C. Martin states about comments: "A comment is a failure to express yourself in code. If you fail, then write a comment; but try not to fail." The source code ought to be clean enough to express their goal with no comments necessary. That said, if there are no code guidelines in places, you cannot blame your coworker, but I personally agree it's unprofessional.

Having been a manager myself and after reading umpteen books by John Maxwell and Les Brown, the only advice I'll give you is to value and nurture them. Don't tell them what they should do, show them what they should do and they will start following you as a leader. Lead by example, that's what this industry truly lacks.

It's gonna be a bit inclined to game development, but here is my list: Node GitHub Auth0 Webpack React Phaser Pixi EZGUI

Uncle Bob, John Romero, Douglas Crockford, Addy Osmani, Paul Irish, Andrzej Mazur and so many others.