title: How to use koala gem to delete Facebook comments
body: <p>I am trying to use koala gem to delete my own comments on Facebook. The comment id is correct and I can delete it in Facebook graph explore. And the authentication part works because I can post,put_like and delete_like.</p>
  
  <p>When I try:</p>
  
  <p>graph.delete_object( @comment_id ) it showed this error:</p>
  
  <p>type: OAuthException, code: 1705, message: (#1705) Selected wall post for deletion does not exist. [HTTP 400]</p>
  
  <p>btw: my rails version is 3.2 and koala version is the latest one.</p>
  
  <p>Anyone could help? Thanks a lot!</p>