Just some thoughts :
In practice, we'll probably want longer randomized delays before coin
withdraw transactions have officially cleared. We do not want
customers spending their coins instantly even if they withdraw
instantly. I suppose this leaves more leeway for the mint to be a bit
slow, not sure if that matters, but presumably the timeouts in the
paper could be increased.
I didn't change section 4 nearly as much as I expected. Initially, I'd
wanted to make the coin language more consistent and more clearly
distinguish preparatory stages from the actual protocol, but I did
neither in the end. Both might still be a good move.