User blog comment:BertH/Layout and navigation updates coming October 3/@comment-4528041-20120920151403/@comment-3030984-20120920152047

Jeez... less shouting please.

As Bert explains above:
 * Site performance: With both the older and newer styles as an option, the JavaScript for both styles must be loaded regardless of which one is enabled. With a single option, loading time will be reduced and site performance will be improved.
 * Better user interaction: Our click tracking shows more frequent use of the custom items on the wiki navigation for wikis with this newer style.

On top of this, the engineers have to maintain two entirely different navigation systems.