He takes the notebook back and this time nods. "Much better. I suppose it makes sense, that you would not have heard our language for so long."

After all, it died out with their people. And Hythlodaeus already knows that the Warrior of Light and his friends were speaking an entirely different language, though he had understood just fine. He supposes perhaps the Dynamis in the area conveyed their words' meaning...?

In any case, Emet-Selch doesn't know that, so it's not worth bringing up. Instead he smiles a little as he pointedly makes a note of speaking in their tongue.

"And how does the creature deal with poisoned aether? Does it take it to a safe location to disperse it, or does it simply purify it?"