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I'm new to the X myself but think I might point out a thing or two. You have the options under System Preferences / User Info Settings to set name/password limits. Default is strict alpha/numerical. You can choose Strict, Medium, or Light (allows multi-byte). You could keep the login name and password at Strict (more secure?) but the user can still use multi-byte for the rest of the profile like Real Name, Location, Sig etc.
Personally I would keep database naming strictly Latin Alpha. This still leaves the MySQL optional description text fields in any language you want. Comment your settings as much as you can in your language, no problem. Less worries if you keep the database names and authentication at alpha/num. But most of the content is as you wish.