FWIW - Almost every casino in WA state expects the hand signal for surrender, and I have been dealt a card a couple times when I actually intended to surrender. You have to lower your hand to the table to "draw a line", and it can get interpreted as a hit if you have an impatient dealer.
Although this is an advantageous situation since if you improve your hand, you can let it go and if you bust, you explain that your intent was to surrender, I would not advocate purposefully trying to give the dealer mixed signals. Ambiguous hand signals are practically guaranteed to draw attention to you from the dealer, the pit, and very likely surveillance if the pattern continues. I also personally believe that purposefully giving unclear hand signals crosses the line between advantage play and cheating.