This topic came up some months ago. Many members wanted to know why people get banned, and suggested a thread were bans were announced. IIRC ioi didn't like the idea of a "wall of shame", but implemented the ban reason field in a banned user's profile.
He's free to do what he wants with his site, but I don't think the current system works very well. Mods have next to zero accountability unless someone really raises a racket for questionable bans, and the limits of how far you can go are really vague from a user's point of view.