Right now there is no such feature like that from where you can know who voted up a certain article. Go suggest it in the forums, if you want to.
But we already have many other features like "Feedback", FB Like, etc from where we identify the popularity of an article. Also there is more chances that if a reader likes your article he will FB like rather than using the vote up or vote down. If they don't like they will just close the page.
The vote down and up feature is just one of the internal metrics so as to calculate hubscore and authorscore.