Luxury
On the Central Continent, it was not uncommon for certain shops, restaurants, and other private services to have stars on the walls of buildings.
Despite not being seen in all establishments nor being extremely popular among spiritual professionals, such a thing was still used by some people. That is because each star represented a rating, which that establishment had achieved through its owner.
In other words, a location with 4-stars would represent a service provided by a low-level grade-2 specialist. As for the case of the restaurant in front of Minos and Abby, this place was managed by a high-level grade-2 cook!
And for some people, such a thing acted as an advertisement for their establishments. After all, even if the inhabitants of a city probably knew about these high-quality sites, the same couldn't be said for visitors.