Allow 2D sprite to receive light from any direction and show on both sides

While my sprite is using the Sprite>Diffuse shader with cull off, giving it the same lighting on both sides of the sprite, the sprite seems to behave strangely depending on where it is in relation to the light source.

Here is the behavior which is difficult to describe: http://i.imgur.com/bkI4iYe.gifv

I would expect the skeleton to be lit on both sides of the fire, however, he is only lit on one. Honestly, I wouldn't mind if only the side receiving the fire's glow lit up. But the current system doesn't make sense!

Thanks for the help, guys!