Did you see 'Nobody'?: When 'nobody' should be understood as non-referring but is understood as referring (i.e. 'Nobody')

From Lewis Carroll's, Through the Look Glass, Chapter 7

[White King:] "And I haven't sent the two Messengers, either.  They're both gone to the town.  Just look along the road, and tell me if you can see either of them."

"I see nobody on the road," said Alice.

"I only wish I had such eyes," the King remarked in a fretful tone.  "To be able to see Nobody! And at that distance, too!  Why, it's as much as I can do to see real people, by this light!" ...

"Who did you pass on the road?" the King went on, holding out his hand to the Messenger for some more hay.

"Nobody," said the Messenger.

"Quite right," said the King: "this young lady say him too. So of course Nobody walks slower than you."

"I do my best," the Messenger said in a sulky tonoe. "I'm sure nobody walks much faster than I do!"

"He can't do that," said the King, "or else he'd have been here first.  However, now you've got your breath, you may tell us what's happened in the town."