Look at http://musicbrainz.org/edit/18071238 and click the first artist search link.
http://musicbrainz.org/search?type=artist&method=advanced&query=%22%E6%A3%AE%E5%B1%B1%E3%80%80%E7%9B%B4%E5%A4%AA%E6%9C%97%22

No results, now replace the full width space by a half width space (press you keyboard's spacebar).
Before, when I wrote my userscript, those searches all worked.