Pinterest is adding some new features to group boards that will make it easier to message the group members as well as keep track of what's being changed and who's joining. The new activity feed will show you when a member has saved a new Pin or when a new section has been added to the board. It will also show you when a new member joins. Additionally, when someone saves a new Pin, you'll now be able to respond with a like or a reply, which will start a new thread, and you use an @-mention in order to say something to a specific member.