Feature summary: When the title is modified using {{DISPLAYTITLE:title}}, put the new title in its own span like <span class="mw-page-title-displaytitle">new title</span>.
Use case(s): Any page using DISPLAYTITLE
Benefits: This allows VE (and maybe other tools) to change the title without overwriting the entire header which breaks all events within it and can wipe links/buttons that were added by gadgets/scripts.