Not disappearing, per say, but rather simply not occurring if you do not have the floorspace for them.
At some point down the road, it would be nice for the Brandish line to be able to produce it's expected explosions regardless of floor space (example: 3 explosions in place with an Acheron if you're face against the wall). This would help when triggering explosive blocks, and be extremely helpful in breaking down chests/minerals.
I won't address the combat advantages to having the weapon work as intended at all times because they're self-evident.
Cheers!
Hmmm... Seems like it would give brandish lines a bit of an edge, but I do agree that you shouldnt let those explosions go to waste. But think, if you've trapped a cat in a corner, and your freind comes in with a charged elemental brandish, then the attack is more effective than if he used a charge on a cat in the migddle of the room. I think that the explosion shouldnt be so variable, so it say, pops up infront of you more often than to the side. untill you get to the dual explosions, then one in front, one with more space in front of you. Just make at least one blast more accurate and predictable.