"Rule" is a substantial part of the r/196 subreddit's culture. It is a reference to how the only rule that was imposed by the original subreddit's mods was "If you visit this subreddit, you must post before you leave." (This rule was later expanded so that people with NFT avatars would get banned because NFTs are bad for the environment, but that's a topic for another day.)

This community we're on now is supposed to be the unofficial(?) continuation of the r/196 subreddit. This community's mods have created more rules to improve moderation's transparency, but the idea of there only being one rule is still fresh in people's minds.