In luxury restaurants or fine dining establishments, it is generally considered impolite or inappropriate to pick up sauce from the plate with bread. Luxury restaurants often have specific etiquette and table manners that guests are expected to follow. Using bread to mop up sauce is generally seen as a casual or informal practice and may be considered inappropriate in a more formal dining setting.
In upscale dining establishments, it is more customary to use utensils, such as a spoon or a knife, to enjoy the sauce or to request additional sauce from the server if desired. The bread is typically intended to be enjoyed as a separate component of the meal, such as an accompaniment to the dish or to cleanse the palate between courses.
However, it's important to note that dining customs can vary depending on the culture, region, or specific restaurant. If you are unsure about the appropriate etiquette in a particular establishment, observing other diners or asking the waitstaff discreetly can help you navigate the dining experience with confidence.