N3733 GB-11 says:

17.5.2.3 [objects.within.classes] defines the use of "exposition only" in the library:
The declarations for such member objects and the definitions of related member types are followed by a comment that ends with exposition only,
28.12.1 [re.regiter] and 28.12.2 [re.tokiter] have members which are preceded (not followed) by a comment ending "exposition only".

It goes on to propose:

Reformat to follow 17.25.2.3