User blog comment:Sarah Manley/New Editor Scheduled for Sitewide Release/@comment-5473581-20110908003658/@comment-126761-20110908132713

The lack of autocomplete is certainly not an intended improvement - I want to get that back in ASAP.

We tied the visual/source mode of the category module to the edit page to ensure people had access to direct category code without having two separate source switches on one page.

The reason you can't disable it completely when the visual editor is enabled, is that the visual editor relies on it for category work. (And I know that's not ideal).