I'm pretty sure the FEers of the forum used to get just as annoyed with sceptimatic as you guys do, but I think they've given up and just scroll past his posts, and many of them stopped posting here altogether. The problem is that as long as he isn't breaking the rules, there's not anything that can be done to stop him from attracting all this attention. As soon as he posts in a thread you guys pounce! I'm not sure why, because you know there's nothing you can post that will work to draw him into an intelligent conversation. Pointing out all the flaws in his arguments only causes him to double down. I know he does break the rules from time to time, and I am aware of him being banned a few times for it, but posting his "theories" isn't a rules infraction.
FES has an easygoing moderation policy, you have to do something pretty terrible to get a serious ban, and I don't remember the last time someone was permanently banned. I think that for the most part that is a very good policy, because over moderated forums generally suck (FES briefly went through an over moderated phase, if you can believe it). Having a light moderation policy allows for more free flowing conversation, but it also allows for the annoyances... sometimes you have to take the good with the bad, because the good is worth it.