SUBSTANCE OVER STYLE: Matteo Marzotto, who has teamed up with Gianni Castiglioni to acquire Vionnet, hosted a cocktail at his baroque, velvet-lined Milan apartment Saturday night to toast his return to the fashion business – and give an impromptu speech that occasionally skewered his old stomping grounds: Valentino. “I worked with superstars, and they were a little bit difficult,” he quipped in a frank address. By contrast, he referred casually to Vionnet’s new designer, Rodolfo Paglialunga from Prada, as Rudy, and stressed his mantra in the Vionnet business will be that “consistency is more important than bull—-. Sorry to use that word. Nothing will be done just for image.” He also disclosed that he’s close to buying a collection of archival dresses from Vionnet biographer Betty Kirke.