Is Article 15 a dishonorable discharge?
That would fall under a court-martial. Article 15 would give the commander a right to punish the Soldier themselves. A commander could recommend him for a court-martial. A court-martial would probably give him a dishonorable discharge plus a fine and reduction to E-1 and even the chance for jail time.
I would, as a commander, give him an Field Grade Article 15. Assuming he was a Specialist or below, I would reduce his rank to E-1 (private), restriction for 60 days (meaning he could only go to his normally place of duty, barracks, place of worship, mess hall, and medical facilities), forfeit 50% of pay for two months and 45 days extra duty. These are the maximum punishment for a Soldier with a field grade Article 15.
More than likely, he's get medically discharged from this, depending on the commander. Of course, I'm a hard ass officer and I wouldn't do that.