DokuWiki uses UTF-8 (an Unicode representation). This encoding is sent in the documents meta headers and used as accept-encoding in the edit form. DokuWiki itself does no reencoding of data sent by the browser, so if the browser ignores the accept-encoding of the form there may be problems - however all known modern browsers do work just fine with UTF8.
Also see the romanization configuration option.
Except where otherwise noted, content on this wiki is licensed under the following license: CC Attribution-Noncommercial-Share Alike 3.0 Unported