This has been bugging me for the longest while, so I might as well put it here.
Okay, so the first time Shinra and Joker meet, he never tells his name to Shinra. “Joker” becomes a nickname that the Fire Force gives him as a potential enemy, because of the card motif and whatever.
Then, later on, Victor refers to Joker by that name. Suspension of disbelief shaky at the moment - maybe it’s like Kira from Death Note, where he just adopts the nickname for convenience. But then we get his flashback... where he’s called Joker before he even met Shinra. How does that work?