As abrupt and sometimes mean WvI can be, he rarely if ever abuses his powers. Most likely you did something that violated the rules he set out for that particular board, so he banned you. Probably not a permaban. If you ask him politely, he'll probably tell you why he banned you, so you won't do it again. Don't argue or accuse, simply ask. If you have any problems with what he tells you, then you might have something that someone could look at. Until then, your next step is up to you.
You haven't exactly presented a case against him that suggests he overstepped his bounds as moderator, and as such there is no reason for anyone to interfere. Talking to him directly is your best shot - find out what you did wrong and how to avoid it happening again.
He was banned from the forums because he was bitching, not roleplaying. When his general attitude changes and he gains an ability to roleplay, the ban will be lifted. Perhaps he can go to the WS boards and get some training.
He posted a pure complaint post of moderate size into the Meeting Hall. The post was definitely not IC and it had not one single roleplay portion. It consisted only of attacks against the Ismays and the leadership of NAO.