i've extracted the unsubscription thing having the same problem ..
here is the test i've used:
(open firebug/dev-console to track XMPP transfer)
.. creates two subscriptions one for 'test' and one for 'another'
.. if you unsubscribe from one it stops getting updates for the other too.
below is an unsubscription including the subid:
TestApp.hx:44 : Unubscribed [test]
seems to be a bug on your side or i am missing something
.. but i don't know what ()