personally i feel that the happy medium between “zuko knows zero cursewords” vs. “zuko knows cursewords that would send toph into frenzies of delight and cause aang to astroproject himself straight to the spirit world” is “zuko can, if suitably provoked, swear with the mouth of a sailor on leave, but would never dare curse in front of iroh because he’s been brought up to have better manners than that, and shocking and disappointing his elderly uncle by the liberal application of foul language is a line that has not yet occured to zuko to consider crossing” with the addendum of “and zuko learned the filthiest and most shocking turns of phrase while listening to iroh playing pai sho with lieutenant jee in the boiler room when they thought he was asleep in his cabin”