There actually is
a proper use for a twisted wire snaffle bit. Often a trainer will use one for a while when re-training a horse that has become insensitive in the mouth and responds poorly to cues on the curb bit. If you have a horse that is becoming "hard-mouthed", or begins to tug against the bit when you put pressure on the bit, you can switch to a twisted-wire snaffle for a few training session and again teach him to give to the bit and flex at the poll, like he should have been doing all along. Yes, it causes him some discomfort in the mouth. That's what it's for. It teaches him that it hurts to pull back against the bit and that it feels much better if he flexes and gives to the bit. Once he's responding as he should, you go back to a less aggressive bit.
Just like with spurs, or any other training aid, there is a proper use and a proper way to use them.