"Because your template - fifteen-ish other times versions of you have come to exist that I and people I know have run across - you guys have lousy childhood situations, except the other one I also grabbed. Also, if I left you where you were, you were almost certainly on-track to eventually fall into obsessively unrequited love with a costumed superhero and terrorize a city for her - or possibly his, in that world - attention."

("Fifteen-ish" is accompanied by a largely cosmetic hint about what sorts of things could constitute "ish"ing a number of Jokers: the situations with daemons, Sue's fork, Aianon and Ansharil. It doesn't so much convey this information as that the "ish" represents actual ambiguity about how many of him there are in circulation, not ignorance on Elspeth's part.)