Don't take this as admin-bashing because it's not (well, mostly) but what's going through your staff's minds when they kick somebody for subpar English? These players aren't logging off for a study session on Rosetta Stone: they are fundamentally unable to grasp the language. Unless you're going to open up a server-sponsored ESL school, they're just going to come back and continue dragging down the standard of roleplay with incompetence.
I understand that they're only a fraction of the non-RP problem but it's still a prominent issue that needs to be addressed if overall standards are expected to return to previous levels.