Yeah Fantasy authors are pretty bombtastic! I have never read Patrick Rothfuss and have only recently read Brandon Sanderson but you have to love when two authors can have fun with each other. Rothfuss started the sign off when he signed "more majestic than Way of Kings" and Sanderson responded with "1000% less sex with random goddesses than Wise Man's Fear". When Rothfuss posted this on Facebook he added a much deserved "well played" to the tag. Now that the battling is over they can return to being friendlies--or whatever they were before.
What's the point of being a super writer if you cannot have signing duels with other equally cool authors!