And not much, as far as I know. You can't ban IP addresses themselves, you can only ban someone with a user account. To prevent Newton from trolling here, they'd have to remove anonymous commenting entirely.
I think it would be possible for InsaneJournal admin to ban someone using a particular IP from posting, but considering the site is run by just one dude and we're moving soon anyway, there wouldn't be much purpose in it at this time.
I suppose it's possible that DW might allow for the option of moderators banning a particular IP address, and if they don't right now, perhaps the DW people might take the suggestion into consideration.