Comment 36 for bug 434733

Everyone agrees that you should be able to the master bug that your bug was made a duplicate of. The problem is that some people and the Ubuntu apport bot are complete and utter inconsiderate bastards. Fixing this is difficult because it will break Ubuntu's bug management. Ubuntu needs to change its bot.

See http://blog.launchpad.net/general/bug-linking-part-2 which discusses the special cases needs to support duplicates properly.