I'm sure Tony cleared the Feech situation up with other families, particularly the Lupartazzis. Tony would have had to kill Feech to banish him. So, instead of killing him, he banished him by sending him back to prison. If Tony made it clear to other families that his plan A is to kill Feech, which he was in his right to do, especially after robbing the Freid wedding, then I'm sure they'd accept his logic that banishing him to prison was a humane alternative to killing him. Let the old man spend his final years playing cards and telling his stories in the can. I could see Tony selling this.

Gambino and Costello setting up Vito Genovese is a good example. Pretty much the same scenario. Sure, it was technically against the rules, but those who make the rules break them. That's life. Who was going to go to war with the old Luciano and Mangano clans? I believe Lucchese backed the Vito Genovese set up, too.