Spark - unintended effect with chests?

Hello. Apologies if this is not in the right place or already known. I searched and didn't find anything.

This is not quite a bug, I think, so much as an unintentional, potentially exploitable effect.

Essentially, if you stand inside a chest (after it has been opened) and cast spark, the sparks appear to count the sides of the chest as walls, meaning they just bounce around within the confines of the chest. It's possible to stack several casts of this and lure in enemies, which generally causes them to die instantly as a dozen or more sparks collide all at once.