Well, that's it on the Communal Share Language (Baseline). Time for lunch. Not one of his best lectures ever, but not all of his lectures can be.
He did have three extra hours left over on that last Communal Share Language, though, and gave those extra hours to Korva Tallandria, Willa Shilira, and Alexandre Esquerra, if they happen to want to ask him any questions over lunch that could benefit from their being able to still speak Baseline, or if they want to go off and think on their own or review their notes in a way that uses Baseline.
There is a discipline out of dath ilan of learning to optimize reality first and appearances second. Yes and indeed, appearances cannot be neglected in human interactions, especially commerce. But if you want to look competent, one should first ask 'How can I actually become competent?' and then 'How can I signal that real competence in a way that's hard to fake?' Any other pathway is one where you're just getting into an arms race between trying to fake how things look, and other people knowing that and not being stupid and guessing what you're faking.
At least, so it is in dath ilan. In Golarion, Keltham gets the impression, there are more complicated things going on. Complicated silly things. It's not going to be like that around him.
Yeah, asking your stupid questions can make you look stupid. It doesn't make you actually any more stupid. Asking your stupid questions does, in fact, make you actually more competent. And benefits Keltham in his teaching, by giving him any idea of what anyone is thinking.
Keltham is not particularly under the impression that the people who didn't ask any questions, if he could read their minds, were not keeping many equally stupid questions to themselves. If he could read their minds, he would update in a predictable direction, so he is just going ahead and updating that way now; he is reminding his emotions as well as his thoughts to update that way.
Whatever it is that would make silence somehow seem like more a good look in regular Cheliax, in a way that's a stable equilibrium of incentives - maybe because what you're really showing off is your prudence or your self-discipline? - it's not a signal that Keltham knows how to read off from their quiet and their controlledly cheerful expressions.
Welcome to Civilization. The equilibrium of your incentives here will not be silence.