How to affect how Facebook app links get munged on a wall?

Question

I got asked this question today, and couldn't find any commentary on this behavior anywhere.

let's say I have a Facebook app, with a URL of http://apps.facebook.com/my-app.

let's say that app points to a canvas page of http://my-app.mydomain.com/

When I share the link to http://apps.facebook.com/my-app on my wall, FB automatically changes the link to http://my-app.mydomain.com/. I can manually change it back, but I was wondering if there's a way to affect the behavior, especially from the app settings?

Likewise, is there a way to affect the text that shows up in the description of the shared items?