I've never been a mod or run a message board, but I think the answer to the question is pretty obvious. It's a warning (not to mention, if he signs up again he may have to choose a different username - but that's speculation).
That said, I have no idea what caused the ban, but in my time here I have noticed that "Snack" gets more than his share of unprovoked crap from people. Like I say, I don't know what happened here, but if this is like other instances I've seen I feel like someone should mention that it seems a little disingenuous to turn a blind eye toward a person who doesn't technically break a rule, but deliberately goads someone else into breaking a rule out of pure mean-spiritedness.
I'll reiterate that I don't know what he did, so take what I'm saying with a grain of salt, but the guy's just about always good-natured. He doesn't mind answering newbie questions that have been answered a hundred times before. In fact, the only times I've ever seen him act any differently is when he gets exasperated about someone being mean to him for no apparent reason.