| Quote #1 For though that Absolon be wood or wroth, |
This quote says that Alisoun wouldn't even notice Absolon if he were crazy, so distracted is she by Nicholas. Madness here is held out as the ultimate attention-getter, a condition that makes a person into a spectacle one can't help but gawk at.
| Quote #2 This knave gooth him up ful sturdily, |
The servant's banging and hollering upon Nicholas's door "as that he were wood" (as if he were crazy) is a foreshadowing of the madness John thinks he observes in Nicholas, and later the moment in which Nicholas and Alisoun run shouting into the streets.
| Quote #3 And at the laste he hadde of him a sighte. |
A common superstition in medieval England (and today, for that matter) was that staring too long at the new moon would make you crazy. The image of Nicholas sitting bolt-upright, staring straight ahead is pretty creepy; you can understand why it would freak John out.