If you notice that your leads have an alert showing they may have joined, it means that another chapter in your community marked that lead as "A+ - Joined." 

The specific chapter is not shared. It simply tells the other chapters that this lead may no longer be a good fit.

If you want to learn more about this feature, check out the overview and FAQ. 

Summary

If you notice that your leads have an alert showing they may have joined, it means that another chapter in your community marked that lead as "A+ - Joined."