SK53
(SK53)
2
Firstly: this is a specific issue related to Italy (but increasingly to CH, FR and other countries where commune mergers occur frequently).
Secondly: the OSM Standard Carto-CSS style is just one example of how the underlying data can be rendered and has to make compromises between a wide range of different styles of mapping & administrative structures in order to produce a consistent style for the whole world.
Thirdly: a number of local OSM communities have their own rendering suited to their particular needs (FOSSGIS in Germany, osm-fr, osm-ie, minority language renderings (Breton, Occitan, Welsh, Irish) etc).
So broadly the answer is to work on a local rendering for Italy which behaves as expected for Italian users.