User blog comment:Sarah Manley/New Editor Scheduled for Sitewide Release/@comment-1158076-20110909012821/@comment-126761-20110909101913

I believe he's asking about the 'add category' option on the saved page, not in the editor - in which case, it's a technical restriction when editing from 'view mode' (quick example, it's difficult to know if a category came from a template, rather than directly in the article)