MOTHERFUCKER! They did it! They fucking DID IT! They retconned their stupid mullrat klingons to only have been shaved! FUCKING YES!!!!!! Do they still look somewhat weird, with too much make-up and weird hands? Yeah... But are they believable as "our" klingons? Abso-fucking-lutely! I love it! I really, really love it! Takes away one of my biggest grievances about the first season!
This isn't a retcon.
They've been saying since pre-release of Season 1 that Klingons have hair, they've just never been consistent on why they shaved it all off.
One person said it was because it helped them use the sensory organs in their ridges, another said it was ritualistic.