Chain bits (NOT mule mouths or bike chains, chains like the one above, with links) I find are often love or hate. I have had horses LOVE, I mean LOVELOVE, chain bits. Never worked good in anything else. Then I've also had horses who absolutely hate the full mouth feel. We had a colt in training once that flat out would not go in a single jointed, twisted, dogbone, french link, lifesaver or mullen mouth snaffle. Desperately tried every bit we owned. Cowhorses, sweet sixes, etc. He would fight, throw his head, gape his mouth in anything, but he didn't respond to a hack either. My trainer took him out one day and just slapped a chain mouth snaffle on him and holy cow, it was a whole different horse. He salivated, he softened, he relaxed, and he worked. Of course that is an extreme case with someone who know how to use her hands. Obviously if someone is yanking and pulling and jerking the horse's face, it will sore the horse and make their mouth hard.
The moral of the story, chains are not a harsh bit. They do bite more than some mouthpieces but just sitting in the horses mouth it is not painful and it really conforms to the horses mouth. Horses with shallow palates love this. Just because a horse is in a stronger bit doesn't mean they aren't soft. These bits were made for refinement, not control.
Pssh.I didn't pick up the wrong lead
It's called a counter canter...
...A very advanced maneuver.