alt131 - 12:48 am on Jun 25, 2011 (gmt 0)
I think the best response depends on context: Just because you "may" do something because it valid according to the recommendations doesn't mean you "should" write your code that way.
That's well-illustrated by the examples: a negative text-indent is widely supported as a technique to improve accessibility. Using it to load search-engine bait is black-hat SEO that will be penalised by search engines.
Negative off-sets (margin and position) have any number of useful applications. But we've all cringed at such (badly) over-engineered documents that the natural layout has been destroyed to point every single element has to be manually dragged back into the view-port because the content has been sent (as Lucy says so well) "into another universe".
As this is in the context of a cms jelly46, I'd ask the question at two levels.