[Given that he just had an episode in front of Darc and tried to cover it up and the restless itch having his scars exposed stirs in him, he feels especially unworthy of the compliment and totally at a loss to respond. At least the wide-eyed astonishment he can blame on the drugs. The blush was probably inevitable either way.

Shiro picks his way through a response.]

I think... [No, he can't just dismiss it. Not coming from Darc. Knowing what Shiro knows Darc knows now, he feels so much more exposed.] Thank you. I'm really not sure what to say. I'll have to think about it.

[This last addition from stoned Shiro, a person who thinks compliments are incredible serious.]