Everything in http://eel.is/c++draft/time.duration.io#1 can be detected at compile time, so it seems to be a misuse that should new be clear that should use a Remarks: element coupled with the shall not participate in overload resolution wording. Do you think this can be done editorially?

A better solution would be to permit all integral types. I assume this element exists to prevent a duration with a char-like Rep from being printed as a character. Such a change would probably require a paper and not a DR.