I agree that the automatic selection of this chat upon joining the network needs to be a configurable switch or removed.

As OP originally stated, they can leave, disable the new player status. As for the benefit of the Green Leaf marker, that is no different than an experienced player, who has been away from the game for a patch or three, running new content to him but old to everyone else in the duty. It is solved with a simple, "Hey, first time here, any pointers?"