Interesting ideas all around. It may sound like something unimportant, but in the new Dolphin structure it's the single most important link/button, so we do need to get it right.

Thumbs up / Thumbs down - sounds good and easy to use, but mostly as a sign (icon in our case). Also a problem for Middle-East and partly Africa, as mentioned earlier.

How about "PLUS" and "MINUS" then? These guys come from latin and their respective characters are quite recognisable.