For a while it was possible to click on the Messaging History and then fiddle with the URL to actually see, edit and delete your backed up SMS messages. And any changes would sync back to your phone.
http://forums.windowscentral.com/win...8/213500-4.htm
They have unfortunately removed this from the web live.com or outlook.com sites. I am hoping that Microsoft brings it back as an official feature once they are done more fully integrating WP, Outlook.com, OneDrive, Skype, etc... It would definitely be complementary to the personalized cloud strategy they are trying to pursue.