I've seen horses with them, are the necessarily bad/do they hurt the horse? The place I ride at, they use NH methods, and I've never seen them use a stud chain, but I saw a lead rope with one on and one in the tack room (they used to breed and race racehorses by the way), but I've never seen them use one. I recently came across a picture of when they first got this Friesian and were taking pictures of him, they had used a stud chain on him (I heard he was gelded like 6 months before they got him, and he was at least 6).
Back to the main point, do stud chains hurt horses? I hate to sound like the inexperienced pony-obsessed girl, its just that I've never had any experience about them and was just curious to know.