Mine is the volume of their voice. If all that they can do is just talk too loudly with no reason for it and don’t control the volume of their voice. That to me is a sign that you’re a stupid fuck. Because people think the louder they are, the more righteous and attention seeking they are. Than it is to just listen, digest and respond accordingly to anyone talking around you.
This is the main thing I come up with because curiosity is the one thing that keeps ignorance from being a temporary state.