Yes, the three dots mean that all the stuff shown when you click the dots will show up in replies.

With that said, I would disagree that this system is superior to Facebook. Having multiple new threads pop up in Gmail for what is in reality a single thread isn't by itself a good enough reason for me to want to unsubscribe, but having to go back and delete old replies seems a bit much. Was Google Groups considered, as it sounds like this behavior is not an issue with that medium? Facebook's organizer group also seems much more active and more conducive to replies that are anything less than a multi-paragraph reply, and the group can also be searched, similar to email.