jealousy

I think Silvio is an interesting character because he seems to be perhaps satisfied with only the potential to do something rather than actually do it. The fact that he's no longer interested in shooting at the count because he is so non chalant about the duel shows a certain primitive nature to his thought process, but on the other hand he decides that he must seek his revenge upon the count after he decides not to shoot. 

I suppose Silvio could be  considered to be petty in the sense that he becomes involved in the duels with the count because of simple jealousy -- of the count’s “youth, intelligence, good looks, boundless gaiety, reckless courage, a great name, [and] inexhaustible supply of money”.