Found something that will confuse some - I thought it was a bug at first:
From Browse, Post in My Communities - first post listed at this time is from our Beta Test ""I'm In"" messasge
Selected Least Replies Posts in My Communities
Opened the third message listed (Mark Chinsky post from 4 years ago on VMWare), clicked back to discussions button.
The ""Back to Discussions"" will return you to the top of the discussion list for the Community you last opened which was ""General"" for Mark's post, which is not the entire list shown when you first clicked ""Browse"".