I don't think this is an intended feature. I think what's happening is when someone in the same instance as you is on a mission, and does something to trigger ghost dialogue, everyone in that instance hears it. A similar thing can be seen in the dreaming city. I was getting bounties from Petra and ghost kept saying random shit while I was in the vendor menu. It was dialogue from the beginning of the weekly mission. When I started the mission, I was put in with other people, as if it was a patrol instance. Everytime someone new joined, I could hear dialogue between ghost and the corsair. A similar effect can be seen in patrol areas where a public event is happening. When you enter the area, even if the event is on the other side of the map, you get the audio visual cues as if you had joined the event. That same audio visual cue will repeat every time someone new joins the instance. This doesn't happen all the time, but it's happened enough for me that I noticed. Tldr, this release is more unstable than season of the worthy. So don't be surprised when cool "features" end up disappearing after a patch.