>>387414325
>>387414689
The headpat is the VR handshake.

You can try telling people not to headpat you, but it's the default. 
You'll have about as much luck with making people not headpat you as you'll have with making people not handshake you IRL. You can, but people have to know you are serious about not wanting the VR handshake. You'll also probably look rude, because you are signalling that you decline a casual atmosphere.