How come so many members show a "?" name upfront, but have different ones beneath it?

That is a glitch that's been around since the Green days.  It's never been fixed. 

It means NOTHING.  It's just a bug in the system. 

If your account photo has been replaced by a question mark it is a longstanding glitch with the avatars. This has been happening for years. It is not because Yahoo reviews your user activity, because they don't tell anyone if that is being done. A review of someone's account activity wouldn't cause their avatar to disappear from the system either.

It is usually a glitch caused by slow servers.

IMHO this is NOT a glitch

 I suspect Verizo is received g account activity of selected email accounts?and that is why the user name changes to "?" for minutes to days.

 Considering that there IS an active possible spam misinformation propaganda campaign about a new format that MAY be an elaborate hoax, since 1 troll admitted it IS a hoax to catch the gullible 2 days ago. I am not at all surprised. Yes, my use name has gone to "? " briefly today. 

Uh, where did anyone say the AVATAR was?replaced by a "?" The USER Name is replaced by a"?" .why does it last for DAYS, sometimes.