If you get a message like this on your WordPress site:
We’re sorry, but we could not fulfill your request for /wordpress/wp-comments-post.php?for=jetpack on this server.
You do not have permission to access this server. Data may not be posted from offsite forms.
Your technical support key is:
The security plugin Bad Behavior is preventing the comment from being published.
You can either 1) go to Settings > Bad Behavior and select this option:
Allow form postings from other web sites (required for OpenID; increases spam received)
Or 2) you can simply deactivate Jetpack Comments.