We have the same problem with bbPress 2.5.4 and WP 4.0.1 and 4.1…There are no answers and topics appear, but we spam messages displayed 
Did the line 142 commented out in plugins/bbpress/includes/replies/template.php
from -> ‘s’ => $default_reply_search, // Maybe search
to -> //’s’ => $default_reply_search, // Maybe search
What is any good?
-> $default_reply_search = !empty( $_REQUEST[‘rs’] ) ? $_REQUEST[‘rs’] : false;
Sry for my english 