Full UTF-8 plugin adds support for all the UTF-8 characters: 1, 2, 3, and 4 bytes long. Without this plugin, WordPress only supports up to 3 bytes.
WordPress does not support full UTF-8 characters because MySQL 5 doesn’t either.
This means that for example you might add unsupported UTF-8 characters to the content of a post, and all will apparently work fine until the next time you save.
When that happens, any character after the first unsupported UTF-8 character will be wiped out without notice, and when the editor reloads the content is truncated and the rest is lost.
This plugin enables full UTF-8 support for:
writing, reading, and searching
title, excerpt and content
posts and pages
Download and info: http://wordpress.org/extend/plugins/full-utf-8/