I put my feet in the feet holder pockets conveniently placed under the seat directly in front of me. If there was a designated safe place other than that I have yet to see it.
i find a foot being placed in close proximity to where my face, and hands and food are going to be/at/near rude..I believe that because the foot is contact with the ground/restroom floor/unclean surfaces but I also recognize my own cultural bias because even in onsens and other public bath experiences I don’t like sitting on the lowest shelf because I don’t like feet 12” from my face....
i find it much more disgusting is when people use the airline bathroom in their socks or bare feet ...bleh...do they think that is water on the floor?
Of course I also find it gross here in the US South women driving large SUVs with their feet higher than the steering wheel or propped on the dash if they are a passenger...I always have two thoughts when I’m driving and observe this behavior 1. Yeast infection? 2. What happens if the air bag deploys?