JoshuaZ:

Things to avoid: Do not give a large bill and say "keep the change" even if this is makes a generous tip or makes precisely the tip you want to give.

What is the exact source of this information? In a few years of living in (Anglophone) Canada, I've never heard of this. In fact, once you get the bill and put the money on the table, the waiter will often ask if you need any change. (Especially if the bill comes in that small folder and you close it over the money so he can't see how much you left when taking it.)