Because the other post is so darn long, I'll reply to the comments here.
Yes, Ace has always exhibited nervous and "superstitious" behavior. He paws at dinner time and has done since he was about two weeks old. The day he was weaned he developed the mouth rinsing ritual to replace being able to nurse to calm himself. He would run frantically for a few minutes, then go the the bucket and rinse. He is absolutely obsessed with marking manure piles.
Yes, the stress of his environment could certainly have contributed to this early onset. Ideally he would be out in a large pasture playing with colts his age, but our set up, and the new owner's set up require individual turnout for set periods of time. We tried several times to buddy him up when he was first weaned, but he was so aggressive we worried he would hurt the subordinate gelding and we were certain that Grey would hurt him trying to put him in his place. He has always been in sight of other horses, and allowed to visit but never got properly socialised. This set up has worked for 6 other Saddlebred or half Saddlebred colts. And it is also how my Grandmother raised half a dozen so while not ideal, it isn't the direct cause of Ace's issues, but an exacerbating factor. We knew within a few months that we really had our hands full, as he was far more tricky to handle than anything we had ever dealt with. Not dangerous just... tricky.
Ace's current owner, who bred his dam and dealt with many of these related horses, has had two or three self mutilators, and can name two stallions in his immediate ancestry who had it, but nothing this extreme. On the other hand, I worked with a half bother of Copy's and a full brother and neither of them showed signs. We owned her 3/4 sister and she was fine and produced all "normal" foals. I believe this is pretty common in Saddlebreds but not talked about, like several congenital issues we have in our stock. We owned another unrelated Saddlebred mutilator who had a lot of mental/emotional issues. I spoke to another ASB pbreeder last evening who had an extreme case, but she had to put the colt down at 10 months because of Wobblers (also a nuerological condition) and I wonder if those syndromes are somehow related.
Even Grey shows some signs. He is a slight "head shaker" (which is a more common equine nuerological Tick) but not enough to be a problem. He can't stand wearing a shanked bit because it tickles his whiskers and he will stop repeatedly to rub the bit against his chest, and sneeze violently... so he wears a snaffle and will never be a saddle seat horse. If Grey feels stressed, he will lick his chest... usually when he is having his girth tightened. And he nickers a low nicker very often, especially when startled, which, after reading up, sounds sort of like the uncontrolled vocalizations of the equine tourettes.
So, reading these articles at least gives us some understanding, puts alot of old puzzle pieces together, and gives us a direction if not answers. However, I can say that Ace will not be spending his life on Prozac. Only time will tell the outcome of this.