In my app, I want to give the user the opportunity to add some comments to a listed item. Rather than showing a "add comments" button, I want to show a little icon. Being lazy, but also, using the visual language of a Mac user, I would like to use the the icon of the TextEdit application. What would Apple think of this? Obviously, I could design something myself, but that is another topic.
I would absolutely stay away from this. Since apple runs the approval process for iPhone apps they might reject your app for infringing on what would probably be copyright or trademarked work.
From a visual perspective, I do not think the TextEdit icon would be best for an "add comments" icon. It seems too general. I think your best bet would be to design something yourself or find a royalty free image online.
I believe this would be copyright infringement unless you had written permission from Apple. They have a copyright and trademark policy posted.
Apple rejected an update to my application because this icon (center), drawn by a designer for me and having no copyright whatsoever by Apple, depicts an iPhone.
I wouldn't push your luck. Stay far away from Apple's IP.