Punctuation for advanced learners

I proofread a book for a client. Before we started going through the corrections, my client asked me if I found any mistakes. I said that there’s no page without, basically comma mistakes.

Client: “Oh my god, I don’t believe in comma rules! Who is it to tell me where to put commas?! …. Well, ok, let’s start. But if I have the feeling that a comma is right, we leave it.”

We spent all together 32 hours to get through 224 pages.