WordPress comments – delimiter “/” not found

I found a soloution and what causes it.
It was not really the delimiter that was the problem it was becasue a user made duplicate posts.

Solution:
Replace

$notify_message .=  preg_replace('#[\s]+#', ' ',sprintf(    get_comment_meta($comment->comment_ID, 'title',1))) .' skrev:'. "\r\n" .       $comment->comment_content . "\r\n\r\n";

With

$notify_message =  preg_replace('/[\s]+/', ' ',sprintf( get_comment_meta($comment->comment_ID, 'title',1)) .' skrev:'. "\r\n" . $comment->comment_content . "\r\n\r\n");

And add following code to function.php in your theme, that will allow same user to make dubplacte post:

    add_filter( 'wp_die_handler', 'my_wp_die_handler_function', 9 ); //9 means         you        can unhook the default before it fires

    function my_wp_die_handler_function($function) {
return 'my_skip_dupes_function'; //use our "die" handler instead (where we won't die)
    }

   //check to make sure we're only filtering out die requests for the "Duplicate"     error we care about
    function my_skip_dupes_function( $message, $title, $args ) {
if (strpos( $message, 'Duplicate comment detected' ) === 0 ) { //make sure we only        prevent death on the $dupe check
   remove_filter( 'wp_die_handler', '_default_wp_die_handler' ); //don't die
    }
   return; //nothing will happen
    }