It would be pretty hard for Chris to surpass Silvio any time soon, so it wasn't jealousy.

My guess is that Silvio, as Consigliere, thought Tony had made the wrong decision in appointing Chrissy acting capo while Paulie was away (note the distance with which Silvio has a conversation with Chris in the parking lot after that meeting). Silvio was simply trying to make Patsy feel he had a bit more power than Tony was making out, perhaps as a way to compensate Patsy for the body blow (Patsy would have been expecting to be acting capo, not Christopher). Silvio gave Patsy the go ahead for two reasons--prevent discontent between a disheartened Patsy and Tony, and to stretch Tony's limits a little as a reminder that Silvio is actually the Consigliere, thus should perhaps have a larger role in deciding who's acting capo.

Mick