The phrase popular science writer would might be useful. It's not super high status, but it is better than blogger and clearly connects to his CFAR position.
Thinking about it a little more I would recommend something like
Eliezer is a AI theorist and popular science writer, known for both his non-fiction and educational fiction explorations of rationality. Including the highly popular Harry Potter and the Methods of rationality.
The new Center for Applied Rationality website has launched! We'll be adding content as time goes by. Let us know if you find broken links, etc.