How to add Spotlight comments to the bundled OS X apps?

I'd like to add a Spotlight comment to TextEdit.app. Is that possible?

What I've done:

• Open Finder
• Browse to /Applications/
• Select TextEdit
• Press ⌘ + I (Get Info)
• Click the lock icon to unlock the dialog
• Click on Spotlight comment text field
• Nothing happens. Even cut, copy and paste options are disabled in the context menu.

This seems to be the case for all the other OS X bundled apps as well (Font Book, iChat, iCal, …)

I could create an alias of the app and give comments to it, but are there any other ways?

You need to have write permission for the bundle. After you open the lock:

• Select 'Read & Write' permission for 'everyone'
• Add your comments
• Restore the permissions