I've known for a long time that satoshi's account was locked (I think I must have read it in a post from theymos) to prevent it from being hacked. If satoshi wants to come back, all it takes is a signed message to theymos and he can regain access.
@satoshi: all it takes is one new post, and I'll send you 50 Merit

I didn't know "locked" also means he's banned though, until I added OmegaStarScream's list to my list of banned users. Most of them have probably been banned for years already, I just didn't know about them until last week.