Or maybe not
Two of my friends with Yahoo accounts have now tested this, and have had no word-substitution problems.
So I dunno if the original article was wrong, or if the "service" has been taken down, or what. But it doesn't seem to be an issue now.
Apologies for the false alarm. 'sfunny, my first reaction to the article was that it sounded like an April Fool's joke, but I figured news.com wouldn't do that sort of thing, especially not when it's not April.