when I first deleted my Facebook account, I decided to keep tabs on it(letting a friend check if she could still see messages we exchanged). For a while, my name was shown as part of the message(but it was black, so you could not click it like a link). I made her check later on and it just said "Unknown user" or so, I cannot recall the exact phrase. Our messages were still there

"Facebook User" is what used to show up on my inbox, for deleted accounts.