Modifying 'New Thread' attributes

[hansolo]

OK so I've added a new template according to this XThreads prefix feature, and it works.

However: to do this I need to add a new entry to a .lang.php file (e.g. "$l['post_cheese'] = "New Cheese";). This feels like I'm modifying the forum software though, won't this be broken if I ever update MyBB? If so, how should I be doing this?