This is now possible but not in the UI. You need to manually put a URL into the browser.

Here's an example for changing post #83833...

http://baseurl/data/snippet.php?snippet=rating&id=83833&content_type=post

You can also re-rate:

http://baseurl/data/snippet.php?snippet=rating&id=83833&content_type=post&rating=6
(rating would show as 3 as actually they are stored as 1-10, even though they are shown as 1-5)

This will *replace* your previous rating.

Note that these URLs will never work as links, only if typed manually in the browser. If a referer is set Composr won't allow it, to stop CSRF attempts to change ratings.