A feral cat sprays in a way incomparable to a cat playing on a couch. They see another cat/dog/person/strange thing out the window and they will spray the door. You come into the house smelling like your friends dog and they spray your shoes. They spray their favorite places to sit or hang out to mark it as theirs. It is a really hard habit to break compared with scratching on furniture. It's not all that hard to train even a kitten not to be aggressive on furniture and it relies on giving them better outlets to scratch on instead, like a good scratching post and plenty of convenient cardboard scratchers, and actively discouraging bad behavior while praising good behavior. You can't really give a feral cat an outlet to spray on, they will spray everywhere they are if they are going to spray at all. It's a territorial behavior, not just rowdy play.
