Currently Gabble's 1-1 text channels only unbind when the other client says <gone/> (or you close the channel), or you receive a message from another resource. This covers two of the three cases in <http://xmpp.org/extensions/xep-0296.html#general-unlock>.
Gabble should unlock when it receives presence from the contact. It should also probably unlock after some period of inactivity.
on Feb 21, 2017 at 05:10:33.
(provided by the Example extension).