code: public static function remove_author_meta_values() {
  		global $blog_id;
  
  		if ( isset( $blog_id ) && ! empty( $blog_id ) ) {
  			$blogusers = get_users( array( 'blog_id' => $blog_id ) );
  			foreach ( $blogusers as $user_object ) {
  				delete_user_meta( $user_object->ID, 'post_subscription' );
  				delete_user_meta( $user_object->ID, 'comment_subscription' );
  			}
  		}
  
  	}
docs: Remove meta data from all users of the blog
  
  @since  0.0.2
  @uses   delete_user_meta, get_users
  @return void