I don't mind a driver mentioning they're not happy driving for Uber and Lyft, or that the rates have gone down in the area, or that they've had a lot of short trips today. That alone wouldn't cause me to rate a driver poorly, though I can imagine that it might for some people.

I do mind when I get a 20-minute rant for the duration of the trip, though. I've had that happen once or twice, once accompanied with a less than subtle "it's possible to tip in cash".