In our case group identities are distinct from the set of current members. The set of current members is important, but the notion of “posts” and “topics” by group members as being representative of the group is less compelling, as people rotate among different groups with some frequency, and even when they are in a group, only some posts by an individual within a group are really relevant to that group.
On the other hand, @mentions of the group are always relevant. I would like to have a link from the card to group mentions. One way to do this would be to have a link to “Activity” and change things so that defaults to the Mentions sub-tab if messages are not routeable.