Jack & Claire meet as family, Claire says he's already joined Locke

As Locke and Jack are making their way back through the jungle, Locke stops and tells Claire to come out because she's been following them. Claire says she was there because Jack is her brother and Locke leaves them to catch up.

Claire asks Jack if he knows that Locke was the one pretending to be Christian, and Jack says yes. Claire says that she never had much family, so she's glad that Jack decided to come with them, meaning Locke's group. Jack says that he's not decided to leave yet, but Claire says that he has. She says that Jack joined Locke whenever he let him talk to him, just like her and the others.

So what is the deal with letting Locke/smokey talk to someone? Does it have real meaning, or is he just very convincing? Richard seemed to break that rule and something tells me Jack will be next.