It should not. Showmanship is about the precision of the pattern, how you present your horse, and the "dance" between you and your horse as you execute the pattern. The horse should not be judged on conformation and should not lose any points because of scars or injuries as long as the injuries do not affect the horse's motion. Now, I'm not saying every judge will hold to that, but you shouldn't be counted off for a scar.
As long as the scar tissue is maintained, there is nothing wrong with the injury (things like basic bad care) it shouldn't influence the scoring of the horse.
Depending on the level and/or your area, it might just influence the score anyway. You can never really tell with some judges, and some people aren't always fair unfortunately. I'd try it anyway. It's something new for horse and handler and can't hurt to try.
Scars will not count against you in showmanship or the riding classes. You could be marked down in the halter classes.
My gelding has a large scar on the front of his cannon bone on his front left. We have ROMs in novice am showmanship (nearing our superior) and amateur showmanship, plus ROMs in lots of other classes. But I can't get a point in the halter class ever.
Thanks guys! I was thinking along the same lines.
Which is why I was thinking of sticking with smaller shows, so that there is a lot of variation in the field. I sort of expect that if she was up against a horse with equal talent, they would place the other one on top.
I will let you all know how it goes!