I'm getting the same problem on Gutsy (pidgin 1:2.1.0-1ubuntu2, pidgin-extprefs 0.7-2). Even if I hand-edit ~/.purple/prefs.xml to set list_visible to 1, it has no effect, and is reset to 0 on exit. The other related settings, e.g. list_maximized, x and y, all work as expected.
I'm getting the same problem on Gutsy (pidgin 1:2.1.0-1ubuntu2, pidgin-extprefs 0.7-2). Even if I hand-edit ~/.purple/prefs.xml to set list_visible to 1, it has no effect, and is reset to 0 on exit. The other related settings, e.g. list_maximized, x and y, all work as expected.