I will often put my feet up in front of me. Not exactly where the photo put them, but more in line with the armrest. And if in a bulkhead seat in Economy that's how I sit the whole flight - with bare feet up the wall. I find it a much more comfortable way to sit and it has a much lower risk of blood clots (something I am high risk for). I would probably not out them where the photo suggested because it might knock the seat in front and I would be far more worried about not kicking his seat than the location of bare feet. I think if the person in front cannot see (or smell) the feet and is not having his chair moved about by them, then nobody else should care. Although Cathay might care that their TV could get damaged.