Right. I think you're both on the same page here. Instead of:
> But for people who under bad firewall, tox must use TCP relays.  

It could be:
> For people who have restrictive firewalls, tox needs to use TCP relays.

Although this kind of contradicts with the previous line. So perhaps:
> #### UDP vs. TCP
>Tox must use UDP simply because [hole punching](http://en.wikipedia.org/wiki/UDP_hole_punching) with TCP is not as reliable.
However, tox does use TCP relays as a fallback if it encounters a firewall that prevents UDP hole punching. ([How it's going to work](https://github.com/irungentoo/ProjectTox-Core/blob/master/docs/TCP_Network.txt))