I have noticed on occasion that a FamilySearch record I have linked from Billiongraves DOES NOT have a source added that would take you to the Billiongraves record. Today I think I figured out why.... It seems to work differently if you are logged into your family search account (Using the "Authenticate with Family Search" button under TOOLS).
Is this intentional -- that is only Family Search users who are actually logged into their account through billiongraves are allowed to change the Family Search info? Maybe users without a Family Search account shouldn't be linking to familysearch at all then?
1) If you have logged in with your own Family Search account... the Billiongraves record is doubly linked. That is, from BillionGraves you can click on "View on FamilySearch" and see the corresponding record. AND when you are in FamilySearch a record that has been linked from Billiongraves will have a source added which you can click on to see the corresponding record in Billiongraves.
2) If you are NOT loggine in with your own Family Search account (and probably it works this way if you don't even have a Family Search account)... The Billiongraves record is only SINGLY linked. That is, from BillionGraves you can click on "View on FamilySearch" and see the corresponding record. BUT there is no source added on the FamilySearch side of things...