I'm afraid I forgot to include this change for the CD and the next WD (N4917), which now only has the __cpp_lib_format macro, without the splitting discussed above. However, I believe the feature test macros are overall editorial in nature, so I would be happy to make the change immediately now, and nobody needs to file NB comments about it? I gather also that there's been new discussion, so could you kindly confirm whether the plan from my previous mail is still acceptable or whether we'd like a different set of macros now?