It would be great if the current chat system just turned into a conversation, as it is, if you send someone a message and they dont see it and log off, when they log back on, they wont see it. Also you cannot send messages to players who are offline.
If you were able to send a message to a player regardless of if they are online/offline (as long as they don't have you blocked), and if they were able to see the message/conversation at any time and refer to it at any time, that would be great.
Another thing is that when you are reading something previous in a conversation if a new reply is written it will auto jump you down to the bottom, if it is possible to not have that auto-jump it would make it a lot easier to catch up on a conversation or re-read something