vote on answer's-answer?

Question

It's nice that users can comment on answers, but it would be nice users to be allowed to comment on answer's answer. (3rd level)

and maybe make answer voting button just text link with "+" or "-" and put it on the right

Answer 1

I thought about fully nested comments, but I think it could begin to lose the nice structure that Q&A engines offer.

As for moving or changing the answer voting buttons, this is easy to do with CSS, if you make a custom theme. I'll add some documentation shortly about how to do this.