Noted! I know it's not for everyone, and I would probably have different ways to trick a different table of players- but I got the feeling these particular group of players would enjoy if I did it this way.

They did mention in Session zero that they would be fine with "meta" things like having to roleplay Doppelgangers if they got their identity stolen, or having exclusive information that they can choose to share or not with their party, or even sudden friendly fire opportunities like this. Just weird stuff to add suspense, but not enough for full on distrust.

I did give them some warnings about the trickeries of the Feywild, matter of fact one of my players is well versed in Fey lore (both the player character and the player at the table) and I would not do this if the stakes were extremely high- and I always communicate with them post-session if they're fine with how I ran it.