@JohnBaez What should the top level discussions be?
I see

* Chapter #
* Lecture # - Chapter #

You mentioned discussions on exercises, so?...

* Exercise #

I also suggest...

* Puzzle # - Chapter # :

I have completed all the exercises for chapter 1. Should I start posting them?
I am also really interested in the responses for your puzzle 4 for chapter 1.
It would nice if they were collected somewhere, should they be in the wiki?