I've been using a neoprene hood for winter kiting, but it doesn't breath. Any hood I find that breathes and fits under my helmet also lets the wind blow right through. What will keep the cold out, fit under my helmet, and won't turn into a wet, smelly mess?

i use buff under my smith snow helmet.
original buff up to -10C/14F and polar buff if it is colder.

http://www.buffusa.com/sports/collections/polar-buff-reg/styles/filter/men/snowboarding/tubular

http://www.buffusa.com/sports/collections/original-buff-reg/styles/filter/men/snowboarding/tubular

How is your head cold, kiteboarding is a vigorous activity, a hood would make me overheat.

But if you're cold buy a balaclava.

In conditions where exposed skin is going to freeze and turn black and blue, yes, I need head protection, no matter how active I am.

When it is that cold, I wear a super thin synthetic beanie hat or balaclava. Super thin to fit under my helmet that I wear all the time. I use a skate style helmet because ski helmets are too hot for me anyway. Super thin! JR