A good start, but I think it misses the things I like about rapportive. The most important thing in rapportive, IMO, is that you see a picture of the person you're responding to. That causes you to respond to a person, rather than just a "user" or "email address" - it forces you to acknowledge the person at the other end, and encourages empathy for them.

This should automatically tell me the person I'm responding to if possible, and show me a picture and context then. A picture (or gravatar) next to their username would also be cool.