That's the best compliment, ever.
This replaces my college years best compliment ever, which was "yes, you are a romantic, but that's what I like best about you" from another friend, especially since I'm no longer as maudlin.
But having my neuroticism described as "terribly cute" is quite awesome. That the compliment was gentlemanly, well-intentioned, and devoid of skeeze makes it even better.
In general, I don't know quite how to respond to compliments (I am very awkward, which is why typical pick up lines never work for me), but ones about my strange quirks feel more real and valuable to me than any compliment about my physical appearance.