When you defeat a troll, you may return a blame token in your possession to the supply, and/or give another player a blame token from the supply.
I completely agree. The icons at the bottom of the Troll cards actually depict this. There's an image of a blame token being put down (presumably to the supply) and another image of one being taken up (presumably from the supply). Note the absence of an image of a single token being passed from one player to another.