Ah, hello Burn... The way you describe is typically how I ban people. I just manually add their names to the banlist. Unfortunately, I have yet to be able to successfully ban an xbox player who is offline. No matter what I add to the list the only thing that ends up saving successfully and working is a steam64 ID.

It sounds like I need to find an xbox player who is currently on the server and then ban them while in-game, then save. Then I can look at what happens to the text file and how the game stores the xbox ID. So far, everything I have tried related to xbox players just gets wiped. I.E. the game thinks that the format is invalid and deletes it on server save.

Theoretically if I ban an online xbox player then save the server, the server will convert the character name into the format it uses for xbox accounts. This should reveal how to format the xbox account ID to make the ban actually work.

I'll update this once I test it out on some poor innocent xbox player :(