I note also that plain texts created on the iPod Touch can be deleted using a swipe then delete, but once they text is synced with the Mac, it can no longer be deleted?!
This is true and is the same reason why documents created on the Mac cannot be deleted on your iPod Touch.
This is a limitation of our current sync process. You’ll have to delete those documents on the Mac. We are working on implementing a new sync process that will not have this restriction.