I haven't ever seen that done. Even in third person POV, you are seeing the scene from a specifc person's eyes. Mid-paragraph switch is terrible. I don't know if there's a specific writing rule that forbids it. If he wants to carry information from inside another person's head, he needs to "show, not tell." In your example, he'd say "In his excitement, Frank didn't even notice Susan's barely suppressed shudder of disgust."