Minimum quality is constant & non-negotiable. This should be defined clearly and lived without compromise.
However, some aspects of quality (above the defined/agreed minimum) could be considered luxury and are as such ‘promoted’ to features.
For instance, when building cars, you want every car to pass mandatory safety regulations. And it may be your brand identity to have a certain design signature. You don’t want to compromise on those.
But in your range of models, you may have more basic models and more luxury models. Where some non functional parts like finish and robustness are better than the baaic models. Those quality attributes then become features.