When using change.org app in Facebook, it sends to my contacts escaped, not human readable URLs with a private message.
But it's much better to use usescaped URL, as shown on the attached picture.
Also please remember the white page issue, when the browser window has to be refreshed to show the petition instead of the whitescreen.
And as an idea, may be it's good to introduce Change.org's URL's shortening, like goo.gl and so on...
My petition is http://help-in.ru/ZZc