Again, I'm in favor of keeping because of F1 violators. Life would be much harder if you didn't see stuff like this:
HonestPirate: You know there's a 2 million credit fee to use this trade lane, right?
[ROFL]TrAdEr: f u n00b! :) Departing Player: [ROFL]TrAdEr
Now, making it a client side option isn't a bad idea. Alternately, I wold be in favor of putting new player/departing player messages on the right side of the game screen, seperate from chat messages, while still keeping them all together in the chat window. I don't know if that's even possible, though.