Unless you think he's actually breaking a rule, another way should be found to handle this. You could always simply start ignoring every OOC message he sends, or even put him on your actual ignore list. If enough people do that and he stops getting any responses to his OOC spam, methinks he will either get the message or he will leave. Either way, problem solved. If you're feeling kind you could even warn him what is going to happen if he doesn't stop, but at this point I wouldn't feel bad about just cutting him out with no warning.