WordPress at a glance
action is not described

comment_form_logged_in_after action-hook . WP 3.0.0

Fires after the is_user_logged_in() check in the comment form.

Usage

add_action( 'comment_form_logged_in_after', 'action_function_name_342', 10, 2 );
function action_function_name_342( $commenter, $user_identity ){
	// action...
}
$commenter(array)
An array containing the comment author's username, email, and URL.
$user_identity(string)
If the commenter is a registered user, the display name, blank otherwise.

Where the hook is called

comment_form()
wp-includes/comment-template.php 2354
do_action( 'comment_form_logged_in_after', $commenter, $user_identity );

Where the hook is used (in WP core)

Does not used.