Quote: Lord_Percy "The hand off to the face is one I've wondered about for a while. Why is it we allow the attacking player to make contact with a defenders head, but not the other way round?'"
Probably because the hand off is basically a flat of the hand delivered front on to the face/head and isn't likely to do a great deal of damage. Using anything other than the hand (e.g. forearm/elbow) is still a penalty offence.
Most tackles are made with the upper arm/shoulder, which applies considerably more force particularly if swung into the tackle and especially if it lands/wraps around the neck area of someone running at pace.
Basic Health and Safety awareness, innit.