He listens intently. Looks thoughtful.
...Nods, but makes a bit of a face, at the last bit. It's not quite the same apology-head-duck as before; it's flatter, more tired and sad.
"Note that I may want you to have the full comprehension-and-speaking version at some points," he says. "In private, but with people who I do not trust with the entire truth. I - would select for people who will keep uninteresting secrets, if incentivized to do so, and it would not be very suspicious to claim that you can use your Wild Gift, at higher cost, to create a shorter-lasting but more powerful translation effect, and that I am reserving this for important and trustworthy people only."
Altarrin pauses.
(He's thinking that obviously making full use of Carissa's actual magical abilities, and even moreso her engineering knowledge from dath ilan, will require working with people who are fully in on the secret. There are enough people whose loyalties he trusts - and not just loyalties, being personally loyal isn't enough for something like this, but there are still enough people whose reasoning ability he trusts as well. And it's not enough, not to maintain a secret like this for longer than weeks to months, even if they make the incredibly costly tradeoff of not using any of what they learn from her at a larger scale. There are very few people who meet all the criteria of personal loyalty to Altarrin plus the necessary curiosity and general reasoning style, and sufficient political adroitness and existing political allies to avoid being mindread or compulsioned by a – he still doesn't want to call them enemies – a non-ally.
He doesn't want to say all of that to Carissa, just yet, because she's scared, and at least some of that is for reasons that don't apply here - whatever its failures, the Eastern Empire isn't Cheliax - and he may not be incredibly skilled at this game, but he's managed to notice that a scared Carissa is a Carissa who tries to be small, and - she's from a world with afterlives, arriving in a world without them, she's under enough pressure already...
He's still mildly frustrated with the part where they have to pretend to be sleeping together. Moreso than usual. He's not sure why.)