I noticed a new one of these last night when I watched parts of the film real carefully. I have never read anything about this one anyplace, but I almost wish that I didn't see it.
In scene on the mountain when Ennis watches Jack when the horse is spinning around, you can clearly see a man next to the horse who quickly steps back in the bushes. He is clear as day.
I also think their is someone next to Jack's horse in the DE, but I am afraid to look to carefully because I don't want to see him, but the man in the earlier scene is right there.