Next time you are in the saddle, pick a time when you are just finishing a trot then a walk, then come to a halt, and freeze (do not reposition your legs) Look down and see if you one knee is advanced further than the other. Gently lean forward and see if you see the foot, below the knee, on one leg before the other.
I say this because I had the same dander marks uneven on my boots. I found out that I was constantly advancing my right leg over the left. persistant habit. I wonder if that had anything to do with why my old lease horse always preferred me to post on the right diagonal . . .
Thanks! If anything though I think my left leg tends to be the one stuck further forward than my right due to recovering from a huge pain flare in the fall. (This was, in fact, that main topic of my most recent lesson, heh.) It's getting better, though! When I manage to not injure myself in other fun new ways (like screwing up my back earlier this week), that is. Elle is a committed leaner on left turns and I wear spurs now and then as a reminder for her to get off my leg and stay up better and balance when we go in that direction. She *can* do it, but she'd much rather take left turns with a motorcycle lean. Yesterday's ride (sans spurs) was a lot of me bumping her with that heel to say "hey now!" and keep her in a proper bend.