I'm not sure what you mean. We don't strip any tags. If you are looking at this in a browser, it will appear as text. That is not how it is being returned from FeedBurner it is just how the browser displays it. You can see the actual response in the browser developer tools menu.
The left is what the browser is rendering, which is just text. The right is the actual elements returned from the FeedBurner response. You can see all the RSS tags are present.