According to a USA Today article, Mark Hamill told the crowd at a fan event on 10/7/17 to give Carrie the “one-finger salute” as some kind of sign of respect.
"Worldwide, everyone feels that gap she left," Hamill continued. "But we all have to hang in there. And if she’s out there somewhere, we have to give her the one-finger salute. Come on everybody, for Carrie," he said, imploring the crowd to all raise their middle fingers in the air as a tribute to Fisher, 60.
What the heck is that all about? In the USA, raising your middle finger is considered vulgar and offensive, akin to saying “f*** you”.