sorry to disagree with many who have posted But should that guy have sat down in FC, No, but once they did it was up to the FAs to notice that and if it was me I would NOT have Ratted them out.
I guess you All also agree that those who give a $20 to the person who is checking them in at a Hotel in order to get a Suite or an Ocean facing room, is Wrong after all had they stayed with that Chain or Hotel often they would get it that way. Yet I dont recall seeing even 1 post in the LV forum telling people its Wrong to Bribe the person, instead everyone is telling everyone how and when to do it and get away with it.
I'll also take it that nobody here Ever took a friend or family member NOT on their same Itn with them down the Blue Carpet, in order to board early and to beable to stow their things. Or for that matter never took them on the Priority line for TSA and say 'they are with me' when they arent on the same itn.
Its the job of the FAs to do a count before the plane takes off and to match up the #s with the ground staff. Its not mine, and if anyone can slip into a seat I say all the power to them, heck if the non-revs can do it why not someone else.