I too have received conflicting information, but was in this exact situation last Friday. I was flying on an F ticket that went EZE-JFK-MIA. When I checked in at JFK, I was attempting to go standby on the 5:30p flight. I too was told that I would be behind the upgraders in the AC, but decided to sort it out at the gate.

When I checked at the gate, I was told F was full and that they would only be able to seat me in Y. But then when I heard there were going to be misconnects, I had to be pretty firm with the agent that I should get the seat ahead of any upgraders. He was pretty unfamiliar with awards and said that I couldn't upgrade on an award, which I had to keep reminding him I wasn't upgrading, but rather I was already downgraded and was just trying to travel in my originally ticketed class.

Once he called a supervisor over, she said that I should be listed as a revenue F pax using the priority code RF instead of RV which is for voluntary economy standby.

Once I was listed appropriately, I went straight to the top and I got the last seat.

Because I received so much conflicting information around this though, I don't know for certain that this is official policy. That particular supervisor in JFK seemed to think so, but I don't know if it would work with another agent. YMMV.

The key thing to ask the agent is if you are listed as a revenue F passenger (RF), or a revenue voluntary standby (RV). If you're not listed as a RF passenger, then I would politely request that you are. I had to be pretty insistent, but was polite the whole time, which was when the agent called the supervisor over to help clarify. Luckily it worked out. On a 763 no less! ^