as to first, not sure how one would do that… there is not timestamp on the display name… wp does not record that kind of info either or any history on the changing of the display name… 

also, what triggered the names changes?  user 2 changing his display name will not affect user 1 display name… it doesnt happen…  but if you updated the settings in the admin panel such that we had to cycle through all the users and update, then its a crap shoot (think its by user id) which one occurs first… again, wp does not record any name change history or timestamp the change…

I dont know why you cannot change the admin name display… if you change the other user to something else, then the original one will be available again…  if you have made name changing disabled, then yeah, but you could turn it back on for fleeting second and do it…  In the next SP 5.3 version, we have made it such that admins can still change display names when changing is disabled – its their forum…

the stats at the bottom are cached… so name changes take your stats update time to change…  or are you just saying the stats name display format does not follow the setting vice the actual data changing?  if latter, would have to check and see if we even look at that for stats…

did a little testing this morning…  new users are getting created in the new name format properly for me…  now, per this thread, we have some changes in this area but not sure around this…

one thing to note, the default (as the text and help in the admin panel say) is only applicable if you are not allowing users to set a display name…  if you are allowing users to pick their display name, the default is not applicable and will be whatever wp sets the initial display name to…

also on the stats, if you change the display format, the existing names in the stats are not updated to the new format…  but any new users added do follow the format…  I can open a ticket about updating the existing users in the recent members list on a name format change…

I have now deleted my second user account and managed to change my display name on the admin account by doing what you suggested and enabling display name changing and then disabling it again after I had changed mine, but again it does not change it in the stats, so if you are able to do anything about that it would be helpful

as previously stated, a correct for name display changes to be reflected in the stats has been incorporated into the next version of SP…