There was a time when I was given a bulkhead for medical reasons - I was flying to Seattle for a second opinion and needed to elevate my leg for a good part of every hour to relieve pain. I certainly removed my shoe and I was careful to put on a fresh sock and I wiped the wall before I left with a sanitizing wipe. It might be that a person needs to elevate their leg but, if not, they should keep their feet on the floor - not on a seat, a seat back, the arm of the seat in front or a bulkhead or a window or anywhere else and this applies to children who should have their shoes removed if their feet are going to be on a seat.