Rack::Utils#escape exists, but it is the method for URI escape. The method for HTML escape is Rack::Utils#escape_html. In refered page escape_html is also used, please see http://www.gittr.com/index.php/archive/using-rackutils-in-sinatra-escape_html-h-in-rails/
If you won't have rack-test installed, none of the examples work. So this seemed to be the most logical place to mention this factoid.