WordPress at a glance
filter is not described

comment_form_field_comment filter-hook . WP 3.0.0

Filters the content of the comment textarea field for display.

Usage

add_filter( 'comment_form_field_comment', 'filter_function_name_9937' );
function filter_function_name_9937( $args_comment_field ){
	// filter...

	return $args_comment_field;
}
$args_comment_field(string)
The content of the comment textarea field.

Where the hook is called

comment_form()
comment_form_field_comment
wp-includes/comment-template.php 2392
echo apply_filters( 'comment_form_field_comment', $field );

Where the hook is used (in WP core)

Does not used.