You're gonna be bothered by how cool I am.

Well, even if he is shutting down emotionally quite frankly it establishes an unhealthy relationship dynamic. But, well, when confronted with Cho emotion he feels at the very least uncomfortable. Ginny manages to startle him and make him feel better, and Luna has an instant of comfort. Why these reactions to girls other than Hermione and a shut down with Hermione? Or is it just BS. Then again, the kiss is an instance when numbness can be argued for the entire chapter. Anything in OoTP as an emotional shutdown is highly unlikely as Harry's emotions were everywhere.