Short and simple idea that I'd love to see implemented. Giving us the ability to send a quick note when gifting an item to a friend, or any form of a private message among friends that they'll receive upon coming online again. Character limits and the same chat filters would apply, of course. Players should also have the ability to turn these notes/messages off in their settings - or rather choose who they can receive them from in the first place.
I think this would be a great addition to the game. Personally, I gift my closer friends items often and I haven't been able to play in a few months due to working hours. I haven't caught my group online at the same time as me when I hop on real quick, and it'd be awesome if I could send 'em a quick note letting them know all is well and when I'll be back around.