Usage and Grammar

Q. My question is about this sentence construction: I’m bigger, stronger, and I know more about it. In narration, I would change this to “I’m bigger and stronger, and I know more about it.” But when it appears in dialogue in novels, I’m inclined to leave it as is. What’s Chicago’s take on this construction? Am I right to be fixing it in narration? Thank you!

A. It’s a judgment call. But by editing only the punctuation, you can eliminate the infelicity and retain the original language: I’m bigger, stronger. And I know more about it.