What I mean is, if your flight is scheduled on a plane with 12F, and they equipment swap to a plane with 8F, some F pax will most likely get displaced. This happens on all airlines, but it will probably be more common when the same plane type (which they are used to swapping regularly) comes in both configurations.

Now, the question is, will they handle it properly, with a sensible pecking order for displacements (so that a paying F or P doesn't get displaced while a confirmed upgrade gets to keep their seat), or will they just screw over whoever happens to be in row 3?

I'd hope for the the former, but given how this was handled, the latter is a distinct possibility. So... my advice is, don't pay for F unless row 1 or 2 is available to be selected.