The play-as says "Suspend the effect of ongoing abilities that have a negative effect on those Heroes until this card is deactivated." so I assume it means something along the lines of this: While active, cards like Poison of Dragons or that curse that decreases heroes by 0/2 (or 0/3) would not actually decrease heroes. I also believe that a card saying "hero can't enter battle until healed" would also be suspended while Hankies is out. What I don't know, though, is whether the decreases (like for PoD) still accumulate and would all kick in when Hankies is deactivated, or if it would just begin counting down at that point.
