Or maybe we could allow types or type annotations to be written using only non-alphabetic characters and then ~ could be ~ and @ something like @ and my fingers

Or maybe we could allow types or type annotations to be written using only non-alphabetic characters and then ~ could be ~ and @ something like @ and my fingers won't break from typing. I do prefer having sigils for types that enrich other types to make them obviously different from types that are parametrized by another. Compare ~string to list<string> - the first is a uniquely owned string, the second is a list of string. ~ is an adjective and list is a noun. ~string is a string with such-and-such memory semantics; list<string> is a list that happens to contain strings.