I use last version of Wordpress and the plugin : Awesome Support.

In the code, I have this filter :

if ( apply_filters('wpas_show_reply_form_front_end',true, $post ) ) { 
?>  

    <h3><?php _e( 'Write a reply', 'awesome-support' ); ?></h3>

    <?php
    wpas_get_reply_form(); 
 } ?>

And I want to condition this filter, so in my theme functions.php, I use this :

// The filter callback function for answering a ticket
function wpas_show_reply_form_front_end_callback( $arg1, $ticket ) {
    // .... my logic to get total replies

    if ($total_replies >= 2) {
        // user can't answer more
        echo 'Cannot answer !';
        __return_false();
    }

    __return_true();
}
add_filter( 'wpas_show_reply_form_front_end', 'wpas_show_reply_form_front_end_callback', 40, 3 );

The fact is I can see my echo 'Cannot answer !'; but the filter returns true all the time. Do I miss anything ? I want to condition my filter according to my logic.