Not obvious to me that this is worse or as user-hostile as many seem to presume.

Previously the blue background made the ad result look more highlighted and more prominent.

Now it is just like the other results - not special or better.

Yes, the HN audience knows the visual convention indicates that the blue background represents an ad. Does your everyday user know that or do they assume the blue results are better?

> Does your everyday user know that or do they assume the blue results are better?

Deceptive UI is the issue. By removing distinctions between ads and normal results, you're going from a frying pan situation straight into the fire.