I have a mixed German / Japanese weblog. The database encoding is UTF8, the tables are encoded in latin1 (as setup by the WordPress installation) and the encoding of the website is UTF8.
All European characters are displayed fine, most of the Japanese ones, too except a few characters such as '上'.
These are displayed correctly in the editor but NOT on the rendered page. On the page these characters are displayed escaped. '上' for instance is displayed as 'ä��'.