Game designer Naoki Yoshida has revealed that users of Final Fantasy XIV could go to jail for using mods. The game has strict rules against running the client and third-party programs at the same time, so even if you use a harmless modification, you can be subject to the most serious sanctions.
It is noted that some of the players have already received punishment for using mods that simplify the user interface. He had to sit with his character in the in-game prison for a week of real time. Of course, there is no 100% guarantee that the game will perceive your mod as a cheat, but such a possibility exists.
Note that, despite the payment, Final Fantasy XIV is of great interest to fans of the MMORPG genre from all over the world. The developers even had to stop selling the project for a while, as the studio could not cope with the influx of new players.