Well, it's like this for me (were you playing as Allies?)
That is, if I have the message tab up then NOTHING appears top left. And the message tab fills and you can scroll in it, but if you close it then everything disappears and isn't there when you open it again. Instead the messages that were in the tab appear top left, but I can't scroll those (with page up and down, as before) and after they 'fill up' they vanish and thus all messages are lost forever. The only way around this, perhaps, is to open the messages tab first thing and NEVER close it. Haven't experimented with this yet.
The message system is definitely porked. And that's a potential show-stopper too, I think, especially in huge scenarios.