I think the issue with having a client auto update is malware infecting your wallet via update and stealing your coins..
I also think full automatic updates are a bad thing, whatever the software is. This is especially true with critical libraries/tools.
We were not speaking about automatic updates here, but the notification system that has been implemented in bitcoin itself years ago :
Bitcoin Satoshi client comes with a keypair developers can use to broadcast 'alerts' into the network. Those are relayed to other peers until the alert itself expires (there are other conditions).
Clients matching the alert properties can then display the alert message to user and set the 'error' field so headless users may also see the message.
Fortunately, bitcoin developers did not publish their alert broadcasting client.
Forks coming with no usable alert mechanism reveals something (at least it should).
love you all and best of luck with your endeavors