Comment 22 for bug 761587

Blacklisting system tray icons has been by design for a long time. They purposely removed the ability to edit the blacklist in 13.04. What's been done has been annoying and due to the fracturing of the indicator systems (system tray vs. app indicator vs. whatever gnome/kde are using these days) a lot of application developers have stopped trying to support the many ways to do indicators and just asked their users to make plugins, assuming that popular needs would be solved. Despite being annoying, I question whether this is a "bug" at all. It's all by intentional design.

The plugin that was referred to is Gajim's way of supporting Unity's appindicator system. You can find it Gajim in Edit->Plugins or http://trac-plugins.gajim.org/wiki/AppindicatorSupportPlugin. Since this is the "official" way of getting appindicator support at this time this bug should probably be closed as "won't fix" since Unity won't be backing down on this change.