Deny or moderate ASCII or Latin-1 comments using CommentFilter API
I've converted my "Ban ASCII or Latin-1 comment" workaround (which was an MT2 source hack) into MT3 callback plugin. It'll reduce comment SPAMs in Japanese Blogs effectively, as most of the Japanese Bloggers want to discuss their readers with Japanese. It supports moderation instead of denying, thanks to easy-to-use CommentFilter API.
There could be the opposite way: to ban Asian comments in Latin/Euro/US blogs, which'll be an interesting homework for readers.