Use appropriate force - the game should never cause pain; Trim fingernails before play to prevent scratches; Players with thumb, hand, or wrist injuries should avoid play
Why people argue about this
People often assume that Section 8 allows for any level of force in thumb wrestling as long as it's not intentional harm, but actually it emphasizes using only appropriate force to prevent pain and injury, even if strength differences are noted. The rule is meant to protect players from accidental injuries, especially when dealing with children who might not realize their grip is too strong.