A nonrev should never be asking someone to switch seats, let alone poach a seat and ask the revenue customer to accommodate them. The offending employee should have their privileges suspended for this. I would be writing this in with as much detail as possible to identify the employee involved. It doesn't matter if they are a pilot in uniform - they have no authority to demand anything, they are not crew on your flight, and I would not defer to any request from a nonrev - or a revenue customer for that matter - that leaves me in a worse seat than I had reserved.