No Sony cannot ban Steam accounts. Only Valve can do that. And generally only does it for reasons like circumventing geo-blocks, malicious activities like spamm

No Sony cannot ban Steam accounts. Only Valve can do that. And generally only does it for reasons like circumventing geo-blocks, malicious activities like spamming and scamming, excessive chargebacks. Various types of community and game bans are up to developers, but those apply only to single game.