Another data point. Booked PHL-BTV on 10/14, in one of the preferred seats (Row 2) that would become FC. Seat map shows the ability to choose seats in the first 3 rows for preferreds. Returning 10/18 BTV-DCA in coach, with the first 3 rows being sold as FC (so I'm back in 6). Both flights operated by Republic as E175's.