As far as I know, it doesn't emit HTML. The Rails view layer uses a string subclass called SafeBuffer (http://yehudakatz.com/2010/02/01/safebuffers-and-rails-3-

As far as I know, it doesn't emit HTML. The Rails view layer uses a string subclass called SafeBuffer (http://yehudakatz.com/2010/02/01/safebuffers-and-rails-3-0/ http://yehudakatz.com/2010/02/01/safebuffers-and-rails-3-0/) to manage implicit escaping. I can't look at the diff for some reason (too many redirects), but I'd guess this issue was the result of some logic that was implemented before SafeBuffers were added.