As long as the injury hasn't interferred with a joint, the scar doesn't cause any performance issues (eg. restricting flexion) and there are no long-term soundness concerns I would have no worries about a cosmetic blemish (even on the face).
Even better if the price is reduced because it is a bit ugly - handsome is as handsome does and all that.
But then my horses are primarily jumpers / eventers - if I was into showing or dressage I would probably have a different view.
I bought my sec A with a barbed wire scar just above his hock he injured himself as a yearling, its not so much proud flesh but the fur has never grown back and I have had him almost 8 years and he's 11. He is on glucosamine and will be forever as he has the odd day when it plays him up. I knew about it when I got him and I only paid £60 for him, such a shame as he's very well bred and a very well put together little man, but I probably would have never got him if he didn't have it