Xkcd (angular momentum problem)

[blackwing1]

I was reading xkcd and wondering if spinning in a counterclockwise way (on the northern hemisphere) would actually steal some of Earth's angular momentum and slow it down a bit. Is it possible or does this violate conservation of momentum?

 

[mgb_phys]

The angular momentum of the system = earth+you is conserved.
If you start running you do slow the Earth down as you push against it, then as you stop you speed it back up (or the other way around depending which direction you run in).