IRO description
Bomb (Alt: Demonstration) is a 2nd class offensive skill available as Alchemist and Biochemist.
Throws a bottle of flammable liquid at a targeted location that will inflict Fire property hybrid damage every half a second to all enemies within its area of effect. It has a chance of breaking enemies' equipped weapon. Each cast consumes a Bottle Grenade.

Notes
This skill cannot be used:
Neither next to each other nor on top of another.
Directly next to an enemy or the user.
The damage is increased via ATK cards, and status cards have no effect.

So apparently you can cast it on top of players years ago. I just need clarification on this as if this is a "fixed" bugged or should be a custom.