Japanese rules use territory scoring and treat ko and life-and-death differently in rare positions; Chinese rules use area scoring and a different komi convention; The differences change the result only in unusual endgames, but tournaments always announce which rule set applies
Why people argue about this
People often assume that switching between area scoring (Japanese rules) and territory scoring (Chinese rules) doesn't significantly impact game results in most scenarios, which leads to misunderstandings about when these differences actually matter—specifically in those rare endgame positions where the rule set can make a noticeable difference.
