WordPress at a glance
action is not described

comment_form_before action-hook . WP 3.0.0

Fires before the comment form.

Usage

add_action( 'comment_form_before', 'action_function_name_356' );
function action_function_name_356(){
	// action...
}

Where the hook is called

comment_form()
comment_form_before
wp-includes/comment-template.php 2296
do_action( 'comment_form_before' );

Where the hook is used (in WP core)

Does not used.