Ticking “Away” worked like a charm on xchat-gnome, but unticking it didn’t do any magic.
This turned out to be a bug fixed upstream (GNOME #462031). Grepping the code revealed a rather trivial fix, which on further lookup was part of the Fedora 9 build. I ended up filing a bug report (Fedora #430883).
A package was released with the stated fix, which crashed xchat-gnome whenever one tried to set or unset away:
$ xchat-gnome
(xchat-gnome:9519): GLib-GObject-WARNING **: invalid uninstantiatable type `(null)' in cast to `GtkToggleButton'
(xchat-gnome:9519): Gtk-CRITICAL **: gtk_toggle_button_get_active: assertion `GTK_IS_TOGGLE_BUTTON (toggle_button)' failed
Looking into it, the issue turned out to be variable naming—bad mojo:
gboolean away = gtk_toggle_button_get_active (GTK_TOGGLE_BUTTON(away));
I went ahead, cleaned up the patch, and submitted it. Now I live in peace.
Nibbana.