The vibe-check argument is tenuous at best. Different people have vastly different ideas of what it means to be pleasant to be around. I personally prefer students who are thoughtful and polite, even shy. Some of my colleagues prefer students who make them laugh, something I don’t value very much. If a student goes to Harvard, I know they are getting the offer; if they go to a t50, I know it entirely depends on their grades. Their interview performance feels almost tangential to whether they’re getting the offer.