Originally Posted by
Proudelitist
I agree...unless you are making a claim based on your boarding pass like "Oh, this is really MY seat" or "They must have duped the seat assignments". Then you should be willing to show it to back up your claim.
You can show it to the FA and not the other passenger. It's not always a good idea to show your name and other personal information (like whether you have a Reserve card or your FF status) to a stranger.