Quoting part of the OP:
Therefore, that allows user A to receive payments on completely delinked addresses using only one public address.
Isn't this already happening? Well, not exactly with one public address, but with one master public key. You can create nearly unlimited addresses which aren't linked and there's neither interaction from the sender.
I still don't understand how silent payments improve anonymity. Doesn't Alice still have lots of outputs in different addresses? Didn't she have the same problem before?
I was thinking the same. If Bob can communicate with Alice using her original address, she can send him one of her newly generated addresses and he can send funds to that new address. Silent payments are not needed if they can communicate between each other. Advantage of silent payment would be if Alice receives many payments and cannot reply to senders.
It would be more interesting to hide sender, not receiver. Maybe silent payments together with help of miners can break connection with senders. Let's say we added a rule to Bitcoin that when a sender sends 1 coin to some kind of null address then miner will include that transaction plus new type of transaction without inputs (similar to coinbase transaction) that pays back 1 coin to new silent payment address of the sender that only miner knows. We are assuming that miner will not reveal that information. In case miner cheated and sends coin to somewhere else, the sender probably can raise an alert(I have not thought of all the math) and honest nodes will reject that block. If lots of senders participate it will work like a mixer.