Ghosts sharing a copy machine" is such a perfect way to put it. I mean, at that point you're not being professional, you're just starring in a low budget office horror movie. Maybe the next step after refusing to nod is just communicating through post it notes left on the monitor. That guy transferring floors feels like the plot twist where the ghost finds a new house to haunt.
My old coworker took "professional distance" so literally he wouldn't even nod hello in the hallway. It got weird, @wrent76, like we were ghosts sharing a copy machine. He eventually transferred to a different floor, which I guess solved his problem.