I've heard it both ways. Seach Engine ranking always has been, and will likely continue to be, a bit of a black box. Notwithstanding, that article is a really good read!
I'd say the duplicate content is a more dangerous threat if people come across your spartan WP blog instead of your fleshed out RW site (the one that you're really trying to drive traffic to). By implementing the "Hidden" option in WP privacy, it's another positive step in working towards search engines serving the site that you want visitors to find.
Again, excellent stack. Can't say it enough.