WordPress at a glance
action is not described

comment_form_before_fields action-hook . WP 3.0.0

Fires before the comment fields in the comment form, excluding the textarea.

Usage

add_action( 'comment_form_before_fields', 'action_function_name_1393' );
function action_function_name_1393(){
	// action...
}

Where the hook is called

comment_form()
comment_form_before_fields
wp-includes/comment-template.php 2404
do_action( 'comment_form_before_fields' );

Where the hook is used (in WP core)

Does not used.