Edited Unassigned: Edit Html Source in Html Editor Extender [27878]

I am unable to figure out how to enable this option. In earlier versions, you created an instance of HtmlEditor (not the extender) and you had the ability to switch to the HTML source edit. That no longer appears to be possible (right?). I seem to recall reading something in recent release notes that said they took it away because it created a vulnerability. But... every other WYSIWYG editor on the planet provides this feature. The documentation that I've found still shows how to use HtmlEditor (not HtmlEditorExtender). However, it doesn't appear that you can use HtmlEditor directly anymore.

What's the deal? Why is this so confusing?