Safely concat the ending tag to simple_format or it will be escaped

actionpack/lib/action_view/helpers/text_helper.rb

@@ -332,7 +332,7 @@ module ActionView
         text.gsub!(/\n\n+/, "</p>\n\n#{start_tag}")  # 2+ newline  -> paragraph
         text.gsub!(/([^\n]\n)(?=[^\n])/, '\1<br />') # 1 newline   -> br
         text.insert 0, start_tag
-        text << "</p>"
+        text.safe_concat("</p>")
       end
 
       # Turns all URLs and e-mail addresses into clickable links. The <tt>:link</tt> option