Last Sunday, flight 1516 LGA-BWI was announced as a full flight and passengers were advised to take the first open seat. I was pleasantly surprised that the two seat exit row had one available. I started to sit and a man said that it he was holding it for his wife. I indicated that SWA has a no saving policy and looked to the FA who was standing right there for support. Instead, she said nothing and I had to take a nearby middle seat, not a happy traveler. While disembarking, I asked her whether in fact people are allowed to save seats and she replied "we can't officially say that". The implication was that the official policy is "Don't ask, don't tell".