IMO, len("") should raise OperationHasNoCommonSenseTodayException, just to not confuse unicode newbies. Modern text is not an array, it is a format, a complex format. Zero-width, double-width monotypes, combining, direction marks, normalization, etc. Almost no one wants to know about codepoint details when working with "just input strings", and those who want may use special namespaces for that. There is no point in making len() an alias for unicode.volatile_number_of_distinct_code_points().

visually_empty(s) is okay, len(s) is probably not.