The same thing just happened to me. In doing my daily round of checking my cards on the apps I noticed that instead of Quicksilver it reads Platinum Mastercard. I phoned Capital One right away, the rep advised that just the name changed but the card is still a Quicksilver card earning 1.5% and besides the name nothing else changed - as matter of fact I can still use the same Quicksilver card as before.
I then proceeded to the tell rep that I don't care if they name the card "funny money bunny blue moon card", as long it still earns 1.5% we are all good. 
EDIT: Just last week I was approved for the Walmart card bringing the total of Cap 1 cards between me and my wife to 6 so not sure if that had anything to do with it.
@Larsim wrote:The same thing just happened to me. In doing my daily round of checking my cards on the apps I noticed that instead of Quicksilver it reads Platinum Mastercard. I phoned Capital One right away, the rep advised that just the name changed but the card is still a Quicksilver card earning 1.5% and besides the name nothing else changed - as matter of fact I can still use the same Quicksilver card as before.
I then proceeded to the tell rep that I don't care if they name the card "funny money bunny blue moon card", as long it still earns 1.5% we are all good.
EDIT: Just last week I was approved for the Walmart card bringing the total of Cap 1 cards between me and my wife to 6 so not sure if that had anything to do with it.
Yep they did it to mine too. 
They are gonna get a lot of people calling and asking about this change. Usually it only pops like that during maintenance.
@Anonymous wrote:
They definitely changed it to a platinum, I just got off phone with CSR, said they reviewed account and that I wasn’t using it a bunch after statement closed and downgraded it for annual fee...
Pretty sure it was always platinum.
Plat, QS, QS1 etc are all platinum unless they are Visa Signature, World MasterCard, or World Elite MasterCard.
Name of card versus the level of the network.
