there is two ways to view this...

PRO:
Some people don't like to spit first, because they see it as a disadvantage to themselves, so if you say "No Feeding", then they opponent wont be so hesitant to battle

CON:
Feeding is the most IMPORTANT to battling...that is what is used for personals, and make the punches better. Plus, they clown your opponent and are more creative

To me...IT DON'T MATTER