This one was a bit of a pain to work out what was going wrong. For those who want the ins and outs of what was happening and how this will change, take a look at the linked branch merge proposal.
The short story is that once this change lands only subscribers of a duplicate will receive email about activity on that duplicate. Anyone subscribed via the master bug (be it directly or from another duplicate) will not be notified of changes to a duplicate. Also, there will be much more work continuing on making bug subscriptions better in the next couple months.
This one was a bit of a pain to work out what was going wrong. For those who want the ins and outs of what was happening and how this will change, take a look at the linked branch merge proposal.
The short story is that once this change lands only subscribers of a duplicate will receive email about activity on that duplicate. Anyone subscribed via the master bug (be it directly or from another duplicate) will not be notified of changes to a duplicate. Also, there will be much more work continuing on making bug subscriptions better in the next couple months.