Tie that in with a daemon on the server counting /ignores against the same account. Should the same account receive, for argument's sake, /ignore requests from 50 different players, then the account is banned from communication on ALL servers temporarily until SE can further investigate the matter.

What SE could do with such a system would be to automatically ban RMT accounts within a few batch /tells on a few servers before those accounts got silenced.

Sure, RMT companies can just buy more accounts. But if an RMT company can only send out only one or two batch tells before an account gets banned on all servers, will they have any sort of profit margin left? Even if they could manage to make money under such a system, their profits would surely drop considerably compared to the situation now, where they can create as many characters per account as they can add then delete, knowing it may be a month or three before SE gets back to banning them.