Here's your reason, basically the theming changes in D7 mean the field theming gets bound a lot lot later in the process, so it's not possible to generate the output into a Textarea for you to edit - that said, it is possible that we can come at this from another angle and use tokens instead BUT it means what you see in contemplate admin page will be nothing at all similar to the output.
The Content Template (a.k.a. ConTemplate) module allows modification of Drupal's teaser and body fields using administrator defined templates. These templates use PHP code and all of the node object variables are available for use in the template. An example node object is displayed and it is as simple as clicking on its properties to add them to the current template.
The feedbuttons.module enables a block which shows button-links allowing users to subscribe to your site's feed in their favorite RSS reader (Google, Bloglines, Newsgator, Pluck, etc.).