As stated above, it is technically against the rules, but happens all the time "on tour". Almost every curler at that level does this, the only reason it came to light is because two dudes on the Swedish Team were trying to "throw the Canucks off their game" (which didn't work). Every curler at the Olympics knows this rule violation is a dumb rule that doesn't effect the game at all. I mean you don't have to have a physics degree to know that "gently tapping" a rock that is on the OTHER SIDE of the ice sheet has zero effect on where the rock eventually ends up. These "tiny finger tip taps of the rock" have zero effect on anything, it is just a dumb rule, and all the curlers know it.
It is just "mind games" shit, and that is all it is, they ALL KNOW the "double tap behind the hog line" does absolutely nothing to the outcome of the game. But on the plus side it sure has given curling a ton of publicity, all involved in Curling are loving this shit
And anytime you have "curling fights", I am all for it.