I had to write an extra rule to fix the search result (when you click on a post link instead of the threads link), for now this rule only makes sure you don't get an error and get routed to the right thread, it seems that the #post is not working, don't know enough of this to assess the problem, anyone any idea?
Code:
RewriteRule ^(.*)/t-(.*)-(.*)-post(.*).html showthread.php?t=$3#post$4&is_vrewrite=yes&%{QUERY_STRING} [L]