Makes total sense

he made the weirdest faces during this fight scene

Fun fact: it's theorised that the scream he's doing is a force scream which stunns enemies in fear. Since he is such a powerful sith this could even affect trained jedis, which is why he managed to kill the first two so quickly and with ease.

also since sith draw their power from passion and emotion his faces are likely the outward expression of him working himself into a frenzy of emotion to give himself an edge.