The quality is simply due to perception of the individual viewer is my point.
Any quantitative change, as I wrote earlier, truly does affect quality.
What you perceive as negligible could appear as having more substantial impact to another.
That is not a dig.
Qualitative does not imply subjective.
As an example: back to my ball-behind-the-wall thought experiment. As the ball is rolling, you could replace the observer with an imaginary "ball detector", that can tell you objective facts about what happens to the ball such as "is the ball in my field of view?", or "is the ball partially hidden?". If you just had this detector, you'd see that the ball is visible, then partially hidden, and then totally hidden as it rolls behind a wall. It gives you no quantitative information about the ball, but its results are both qualitative and objective.
Now take what I've said across the past few comments and apply it to the sunset, and come up with your own conclusion: does refraction alter the qualitative behavior of a sunset? Personally I can see no way in which refraction of a fraction of a degree would cause a qualitative change in the sunset. If you disagree, I would love you to tell me why.
Sidenote: large qualitative changes can easily cause quantitative changes. If we go back to the thought experiment, you could change the velocity of the ball to zero, which would certainly be a qualitative change.