WordPress at a glance
filter is not described

the_modified_author filter-hook . WP 2.8.0

Filters the display name of the author who last edited the current post.

Usage

add_filter( 'the_modified_author', 'filter_function_name_5091' );
function filter_function_name_5091( $display_name ){
	// filter...

	return $display_name;
}
$display_name(string)
The author's display name.

Where the hook is called

get_the_modified_author()
the_modified_author
wp-includes/author-template.php 97
return apply_filters('the_modified_author', $last_user->display_name);

Where the hook is used (in WP core)

Does not used.