Without force own texture, imagine that all your objects are gathered in one layer (respecting the their layer repartition for z sorting) and then rendered
If a layer has force own texture on, their object will be kind of baked into one canvas, and then this intermediary rendering will be used instead of the objects (this intermediary rendering is what makes using force own texture slightly slower)
The consequence of that, is that effects are limited to one layer. If you burn hole you can, in a way control which which object you will affect this way.
In your implementation, you put an effect on the entire layer, so it will be applyed to everything underneath.
If an object is in Destination-in, everything underneath its transparent pixels will be erased, else revealed.
Since your layer is mostly transparent except for the few light sprite that are on it, only what's under your light sprites will be revealed, else you'll see the background of the HTML element containing the C2 canvas (gray in the preview)
You see black in the editor, it's because it's the color of nothing (:
destination in totally erased eveything on the viewport.
Try changing the background color of your Lighting or Background layers you'll see nothing will change, the black isn't the color of your Lighting layer (how could it be, it's a transparent layer (: )