In the Faces view, I can tell some are the same face, and want to combine them into stacks. Lightroom wants a name before it will merge or do anything else, it seems. But some items are already stacked all by itself. I naturally tried dragging and dropping and it doesn't combine.
Consider shooting at a party. I don't know a bunch of people. But I can tell faces in profile etc. that are the same. When I get someone to come identify the people, I want to have a clean presentation of one stack per unknown person, not go chasing them around with someone who wants to answer a quick question and leave, not stick around for more fussing around.
Give each stack of photos a temporary name. Woman-1, Bald-Man-1, stuff like that. Or maybe more politically correct than that. "Follically impaired man #1"
Then all you have to do is ask someone to identify each stack. As they do, change the name and you should be good to go. I had to check to make sure, but yes, changing the name on the top of the stack changes them all.