I posted to http://test.musicbrainz.org/ws/2/recording/?client=jaikozngs-3.6.0
this body <?xml version="1.0" encoding="UTF-8" standalone="yes"?><metadata xmlns:ns2="http://musicbrainz.org/ns/ext#-2.0" xmlns="http://musicbrainz.org/ns/mmd-2.0#"><recording-list><recording id="16b61576-b869-4425-8287-e07728557e30"><user-rating>40</user-rating></recording></recording-list></metadata>

It returned this
<?xml version="1.0" encoding="UTF-8"?><metadata xmlns="http://musicbrainz.org/ns/mmd-2.0#"><message><text>OK</text></message></metadata>

But when I look in the UI there are no recording level ratings set.

http://test.musicbrainz.org/recording/16b61576-b869-4425-8287-e07728557e30/details