"Nearest enemy"?

[Vaeron]

That final part is for a very straight-forward reason: if you can't shoot it, you shouldn't be able to quarry it. And if you can shoot it (which you can even if it's invisible), you should be able to quarry it.

Put simply, don't try to place your Quarry if you know there's an enemy hidden behind a boulder nearby (assuming he's closer than any visible foes). However, in this case I will tell you "you can't do that" when you attempt to take your minor action. (This leaves you with your minor action intact - you don't lose the designate action when it would "fail" because of this rule.)

What if there's an enemy behind a locked door you're aware of, but are unable to get to? Are you still unable to use your quarry against that enemy's lackeys who are charging you but further away square-wise? What if you KNOW there's an enemy in his room at the inn, and he's two squares up, but his allies are just coming in the inn door four squares away? Can't quarry them because the guy upstairs is nearest? What if a kobold sees your party approaching and runs around a corner to sound an alarm, and his buddies start heading for the tunnel entrance to engage you? Can't shoot them, because the kobold who ran around the corner is still technically closest?

This rule was erratad for a reason. Breaking it even more helps improve gameplay how, exactly?