The buyer should already receive a detailed receipt from the payment processor (PayPal, Google Checkout, etc.). The thank-you email is only intended as just that -- a way to thank the buyer for their order and, if relevant, provide a link to their thank-you page where we'd provide their download links.
There is a known bug with Adobe's Flash Player 10 plugin for Mac browsers, where it loses any manual linebreaks from pasted-in text:
There is nothing we can do to fix or workaround the problem in the way it affects our Seller Admin. As soon as Adobe fixes this bug, linebreaks in text will suddenly start working fine again for Mac users who upgrade their Flash plugin to use the bugfixed version.