First of all thanks for finding 3, I only tested the code very in very simple cases.
In response to 2, when I am reading lisp code in the format you suggested, I cannot tell whether the else case is actually part of the clause above it or is actually an else case. I just use t to make it explicit that this is the else case.
And I agree with you for 6. We should just extend mac so that it autogensyms the code it is given. There is no harm in doing this since all of the code previously written should still work.
Yeah, I too like not relying on an implicit 'else'. In fact, I use :else instead of t to be even more clear.
This is all most excellent. Don't be afraid to commit and push! Feel free to override the default mac if there aren't any obvious problems. There aren't very many people using anarki, and we can always roll it back later if necessary.