Umm... Jurisdiction of an internet forum is actually not that easily determined in actual law practice. I dealt with a lot of Chinese nationals running internet forums registered overseas who somehow thought they are exempt from PRC law. Turns out they are not always right, but how China likes to do things is a whole other issue.
Given Taiwan's actual level of influence in the world, the effect of Taiwanese law over foreign internet users is practically nil as long as they don't come to Taiwan. Of course he could also choose to sue you under Canadian law if he wishes.
I'm not taking any sides, just to give my 2 cents to a legal topic I actually care about.