What accounts for the softer texture and sharper flavor of Italian ice creams?
There are several major factors that affect the texture of ice cream or gelato in the absence of  stabilizers or gums:


Air mixed in during the churning essentially creates a foam, which is softer than a solid product would be.  While this air may be only 10% by volume, it makes a huge difference in texture.
The churning and rapid freezing also minimizes the size of ice crystals, so the non-air phase is essentially a syrup of sugary water with emulsified milk fat, with very small ice crystals suspended in it.  Since it is not solid, it is easier to cut.
The serving temperature for gelato I believe is traditionally warmer than the serving temperature of ice cream, which provides a softer texture (more syrup, less ice) allows the flavors to be perceived more easily as they are more aromatic at warmer temperatures.
The gelato may contain ingredients with alcohol, such as Franglico in a hazelnut gelato; this contributes a small anti-freeze effect.  Similarly, the pectins from some fruit ingredients will also naturally interfere with ice crystal formation--but these influences are specific to a given recipe.


The lower milkfat percentage makes the flavors in the gelato more apparent, since they are not drowned out by the richness of the diary.