Harvey was a weird ghost. Since he could pass through walls and gravity didn’t affect him, why should he orientate himself that he appeared like he was floating or walking along the floor. Sometimes he’d come in through the wall on the ceiling. Other times he’d come in oriented at some strange angle and approach in an unusual trajectory. Or he just appear and vanish. As for how he could move things or even make sounds, since he couldn’t vibrate, physical vocal cords, he never quite understood that. Or that there was a chill in the air when he approached.