How do I see them as different from one another?
Reacting seems to be more immediate, jumping to conclusions very quickly, and, therefore, this can lead to heated communication. Here there is a lack of wisdom.
Responding, for me, points more to seasoned wisdom, in the sense of not immediately speaking without first thinking through the implications.
For many, this might simply be a case of semantics. But, as I understand communication, these are two quite different words. One is more helpful (responding); one is not as helpful (reacting). This is true in real-life person to person communication and in the midst of the world wide web (we call it the internet today).
As follower of the Christ, I believe we are called to be responders and not reactors, even when righteous anger is called for in the midst of injustice.