The example from the codex, the array of argument is now required.
global $post, $current_user; //for this example only :)
$commentdata = array('comment_post_ID' => $post->ID, // to which post the comment will show up
'comment_author' => 'Another Someone', //fixed value - can be dynamic
'comment_author_email' => '[email protected]', //fixed value - can be dynamic
'comment_author_url' => 'http://example.com', //fixed value - can be dynamic
'comment_content' => 'Comment messsage...', //fixed value - can be dynamic
'comment_type' => '', //empty for regular comments, 'pingback' for pingbacks, 'trackback' for trackbacks
'comment_parent' => 0, //0 if it's not a reply to another comment; if it's a reply, mention the parent comment ID here
'user_id' => $current_user->ID, //passing current user ID or any predefined as per the demand
);
//Insert new comment and get the comment ID
$comment_id = wp_new_comment( $commentdata );
You can have a look to wp_filter_comment(), the source shows some filters that set fill $commentdata. Maybe one of these are used by the plugin you use.