Too late to edit, but: > Equal signs make sense for assignment and equality because of mathy history. But question marks and exclamation marks don't make much

Too late to edit, but: > Equal signs make sense for assignment and equality because of mathy history. But question marks and exclamation marks don't make much sense for nullability. I think they do. The question mark expresses uncertainty ("does this contain an actual String?") and the exclamation mark expresses certainty ("this definitely contains a String!").