to my understanding, CF is not waterproof but the resin used in the casting process is. if you grind a CF sample down you expose fiber thus inducing water to your fibre.
i am in no way an expert on carbon fibre though and have just bought my first CF bike
yes we agree a clear coat would be sufficient. i however said nothing about clear coating your bike, my argument is strictly related to weight saving what i said was that if you sand you bike down and ride it in the rain you are going to fuck it up, and i believe most experts on the subject agree exposed carbon fibre and water is a bad mix.
there is a reason planes with carbon fibre wings have a hard time getting aproved by FAA