Some items, places, powers, etc. can throw the balance of the game off. This makes it too easy for the characters to succeed with the standard rules and processes applied. Typically this allows for some epic level advantages that reduce overall challenges.
Usually it also introduces levels of detail and tracking of elements that are unnecessary minutiae that could slow play. If, by default, materials on the site have an inherent danger in this, they will be designated as Power/Game Balance Issue. This label means “The information herein could unbalance the game, as it could easily be abused depending on the nature of the campaign. Players should not assume it is allowed unless explicitly by the Game Master.“. Some of this reflects the Character Emphasis on gritty realism inherent in the Incarna character approach.