[B]rains were not needed in a society like that, and indeed would have marred it, hindered it, spoiled its symmetry—perhaps rendered its existence impossible. (3.2)
Hank's talking about the knights' tendencies to duel total strangers for no reason at all. Can anything be gained from such a practice besides lots of choice eating for the local crows? Hank doesn't think so (even though he doesn't have anything against crows).
The king and the whole Round Table were in raptures over this preposterous opportunity for adventure. (11.2)
Hank suggests that traditionally heroic actions—like going out and killing ogres—are actually pretty stupid. Is it because the knights could be killed, or because the very idea of ogres is stupid? It would probably be less stupid if ogres actually caused a problem in Camelot, but they seem pretty nonexistent.
"What are you talking about? Don't you know what a map is? There, there, never mind, don't explain, I hate explanations." (11.5)
Hank's talking about Sandy here, and even though he loves her, he clearly has no patience for her foolishness. Her long-winded chattering actually helps Twain point at old Arthurian stories—she goes on and on without actually saying anything… just like Malory.
These big children, their fears gone, became so ravished with wonder over my awe-compelling fireworks that I had to stay there and smoke a couple of pipes out before they would let me go. (14.2)
The Yankee seems pretty irritated at having to wow the yokels here, since it slows him down. Being smart has its downsides.
Her intellect was good, she had brains enough, but her training made her an ass. (18.3)
The book blames foolishness not on individuals, but on culture here… which is a much tougher problem to fix. Sure Hank can educate Sandy (or Morgan, who he's talking about here), and make Clarence his assistant and such, but how does he get the whole society to shift? It takes a little more than remembering when the eclipse will be.
Hank Morgan (a.k.a. The Yankee, a.k.a. The Boss)
"How old are you, Sandy?" It was the first time I ever struck a still place in her. The mill had shut down for repairs, or something. (19.5)
Pretty simple question, but it throws Sandy for a complete loop. And remember, this is one of the few people in Arthur's time who Hank actually respects. How can he handle the rest of the yahoos in this era? Well okay, he handles them by fooling them with his pseudo magic, but still…
I was ashamed of her, ashamed of the human race. (20.8)
Sandy kisses the rescued pigs as if they were princesses. Twain isn't making a joke here—nope, he just makes a sad statement about our species in general.
I drilled him as representing in turn all sorts of people out of luck and suffering dire privations and misfortunes. But lord, it was only just words, words—they meant nothing in the world to him. (28.4)
The king can't understand hardships described to him: he has to experience them himself in order for them to sink in. (You might want to work on that lack of imagination, your majesty…) Twain may be quietly applying the king's tendency to a wider target… mainly everyone who gets set in their ways, no matter how silly those ways may be.
What those people valued was high wages; it didn't seem to be a matter of any consequence to them whether the high wages would buy anything or not. (33.7)
There seems to be a contrast here between Hank's ability to contemplate sophisticated ideas like inflation and the Arthurian subjects who only view things on the surface. Hank wants to change all that, but it takes years. (Lucky there's not a lot to do in the Middle Ages.)
"I reckon we are all fools. Born so, no doubt." (34.15)