Will a person be held accountable for their facial expressions?

Originally, facial expressions are not something a person is held accountable for in normal circumstances. However, they can transform into a sin if the intention behind them is to harm someone, backbite about them, belittle them, or mock them. Allah Almighty knows "the treachery of the eyes and what the breasts conceal." Qatadah interpreted "the treachery of the eyes" as winking or closing one's eye in matters displeasing to Allah. Furthermore, 'lamz' (fault-finding) and 'hamz' (slandering) can be done with the eye, the mouth, and the hand, not just through speech. So, anything through which others understand what the backbiter dislikes, whether it be a gesture, a wink, a hint, or an action, constitutes backbiting.