I have an XML debug log from Pidgin showing them arriving to the client out of order. A sanatized bit of it is here. It is a bit messy, but you can see that the messages are delivered in an order that does not follow the time stamps.
Is that the type of logging you were referring to?
As a data point, users are all logged in to gtalk and then accessing the chat server through those accounts. A mix of Adium and Pidgin clients. All users see history out of order.
If you leave/re-join, the order is different every time
Interesting thing I just learned in capturing debugging points for this. If I access the chat through an account local to the chat server (vs gtalk) it works. So it would appears it might be the server to server interaction, and perhaps specifically the google server.
(16:07:23) jabber: Recv (ssl)(503): Availablel1c32c817853e9050cf5dfff230c93ccff80f6ef91</ph oto>
(16:07:23) jabber: Recv (ssl)(225): This room is not anonymous.
(16:07:23) jabber: Recv (ssl)(273): room
(16:07:23) jabber: Recv (ssl)(381): blah
(16:07:23) jabber: Recv (ssl)(395): blah
(16:07:23) jabber: Recv (ssl)(361): blah
(16:07:23) jabber: Recv (ssl)(369): blah
(16:07:23) jabber: Recv (ssl)(434): blah
(16:07:23) jabber: Recv (ssl)(561): blah
(16:07:23) jabber: Recv (ssl)(362): blah
(16:07:23) jabber: Recv (ssl)(431): blah
(16:07:23) jabber: Recv (ssl)(375): blah
(16:07:23) jabber: Recv (ssl)(379): blah
(16:07:23) jabber: Recv (ssl)(384): blah
(16:07:23) jabber: Recv (ssl)(358): blah
(16:07:23) jabber: Recv (ssl)(431): blah
(16:07:23) jabber: Recv (ssl)(362): blah
(16:07:23) jabber: Recv (ssl)(368): blah
(16:07:23) jabber: Recv (ssl)(349): blah
(16:07:23) jabber: Recv (ssl)(366): blah
(16:07:23) jabber: Recv (ssl)(352): blah
(16:07:23) jabber: Recv (ssl)(396): blah
(16:07:23) jabber: Recv (ssl)(382): blah
(16:07:23) jabber: Recv (ssl)(468): blah
(16:07:23) jabber: Recv (ssl)(414): blah
(16:07:23) jabber: Recv (ssl)(390): blah
(16:07:23) jabber: Recv (ssl)(353): blah
(16:07:23) jabber: Recv (ssl)(372): blah
(16:07:23) jabber: Recv (ssl)(347): blah
(16:07:23) jabber: Recv (ssl)(391): blah
(16:07:23) jabber: Recv (ssl)(367): blah
(16:07:23) jabber: Recv (ssl)(387): blah
(16:07:23) jabber: Recv (ssl)(405): blah
(16:07:23) jabber: Recv (ssl)(357): blah
(16:07:23) jabber: Recv (ssl)(552): blah
(16:07:23) jabber: Recv (ssl)(354): blah
(16:07:23) jabber: Recv (ssl)(361): blah
(16:07:23) jabber: Recv (ssl)(479): blah
(16:07:23) jabber: Recv (ssl)(360): blah
(16:07:23) jabber: Recv (ssl)(379): blah
(16:07:23) jabber: Recv (ssl)(361): blah
(16:07:23) jabber: Recv (ssl)(360): blah
(16:07:23) jabber: Recv (ssl)(395): blah
(16:07:23) jabber: Recv (ssl)(423): blah
(16:07:23) jabber: Recv (ssl)(363): blah
(16:07:23) jabber: Recv (ssl)(500): blah
(16:07:23) jabber: Recv (ssl)(415): blah