Just a clarification about how that works:
When a player deletes, apparently the text of all messages sent by that player get turned into "deleted". The subject line and that it came from that player is still in your mailbox.
I had hopes that the messages were retained, and the text was just being suppressed because the player was deleted. That does not appear to be the case. A friend of mine deleted recently, but then changed his mind and came back to the game. All messages prior to the time of his deletion are wiped. He can converse with me normally now, but everything he sent to me before is gone.
So this is not only an unnecessary wipe, from my point of view. It is irreversible as well.
I have had friends leave, who wanted to send me a last message. But when they deleted before I logged on, I am tortured by the evidence in my mail box that they wanted to tell me something, but I will now never know what.