Son draws in the margins of every school notebook. Do I stop him?

Our 8 year old fills the edges of every notebook page with drawings: small cars, a running cartoon of a cat, faces of his friends. He isn't doing it instead of the work, the work is there and mostly neat. But last year one teacher wrote 'no drawing in notebooks' in red, and a couple of others never mentioned it. I sketch myself and I'm reluctant to make him stop something he obviously enjoys. On the other hand I don't want him marked down in class 4 for presentation, or seen as not paying attention. I can't decide whether to have a conversation about it or leave it to the teachers.