What I find truly rude is when a waiter attempts to clear a plate or plates without asking if one is finished eating, even if food is still on the plate. It's become way too frequent. I'm by no means a slow eater, but I like to occasionally put down my cutlery and enjoy my wine for a few sips. Or maybe I'm in conversation with my dining companions.

In any case, I don't know why staff isn't trained to know the standard "cutlery crossed" means don't take, while parallel cutlery means, please take this plate.