We already have a pop-up window on our chat box now, i don't see why when someone sends us a /tell we can't just click then box and have a /reply option that would automatically set you to sending a /tell to the last person that sent one to you.

Maybe if you could customise that option to store a certain amount of /tell [insert name] in it so you could select one of them quickly and easily without having to type /tell [insert name] everytime you log on. That'd be more conveniant.