Why do so many questions have "troll" in them? is it European thing?

No, it is an internet thing. Trolls on the internet are people that persistently and maliciously post inflammatory content simply to incite the other users. On the YA site it also includes people the abuse the rules regularly in other ways, like thumbs down endlessly, reporting needlessly, multiple accounts for stalking or pointgaming, etc.

Because alas Yahoo answers is riddled with them

its an expression for silly trolls , comme tu, como tu

oui, c'est europeanne

si, es europeano.

i never noticed that :)