add following code in your theme’s (child theme’s if any) functions.php
add_action( 'wp_enqueue_scripts', function(){
wp_deregister_script( 'fep-replies-show-hide' );
});
Update:
add following code in your theme’s (child theme’s if any) functions.php
add_filter( 'fep_filter_hide_message_initially_if_read', '__return_false' );