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I'm guessing that he was his own self, his real self, Qawohl, when he spoke in his native tongue and couldn't get rid of the "Maggot" identity when he spoke in Basic. With the language came a role that he couldn't
overcome just yet: Just look how different he even looks when he speaks in his own language. He's more menacing and younger looking then.
What's kind of tragic is that if Qawohl would have just taken the ship and returned to his people, then Exal could well have won, the Emperor's Children would have been then destroyed and Korriban would have fallen to the Republic. The Sith Emperor won thanks to his decision.