When using MSN, the notice "user has joined the conversation." and "user has left the conversation." is displayed in the chat window, often several times during a conversation. I think there is an idle timeout of one minute triggering a "left" notice. A "joined" notice is then printed together with the next chat-messege sent or recieved.
As these "left" and "joined" notices has no relation to typing-notification or whether the other user has closed his/her chat window they are just annoying.
I suggest having a checkbox to control if these notices should be displayed or not. (Currently I've comment out a few lines from the gui-code to get rid of them.)
And by the way, the GUI does not seem to have an option to set the colour of these notices. They are always green.