It makes total sense not to display a 1 in a circle when there's exactly 1 card of a certain type in a hand, but for a kingdom pile it is very easy to miss when the pile is almost out.
I would also like to have a different color for low piles again. Or even a transition of colors (brightness?) from 10 to 1.
I think putting a 1 on a pile is a good idea, because it's consistent and therefore easier to recognize the state of the pile.
They said in the stream yesterday that the "1" would be coming back.
I like MF's "warning" color as the piles are getting low though. I'd be in favor of switching the colors to be more like how MF's are. Red for low piles just makes sense. No reason to be different just to be different.
One related thing with this is when it's not my turn, the Actions/Buys/Coins counter covers up a lot of pile numbers, so I can't see how close piles are to emptying until it's my turn again.