Several thoughts, some reasonable and some probably stupid, split into separate comments so the reasonable parts can be discussed and the stupid parts torn apart separately:
Part 3. Since the power that the attackers have in these messages is the reaction of the recipient, it might be possible to turn this around. In part 2, I suggested filtering and trashing (or sharing for research into de-anonymizing the senders). How about going beyond ignoring the empty idiots and embracing their idiocy? Make a game of this. Have a scoring systems where you get points based on the number of threats…
Yes, but not by using the mechanism you go on to describe. You simply have to show the harasser that their harassment doesn't bother you. The points system won't convey that to a troll. Worrying about trolls enough to join into such a system validates, not defuses, their efforts.