How is something like this still allowed to continue?

[Kurando]

I don't think it's allowed, ofc i could be wrong.

If players are trading services for Gil then it's generally ok as it's a currency (provided by SE) to use in-game, hence why you can trade it between players. Though if the players are expecting something else as payment (i.e. real money) then that isn't allowed, but as the negotiations generally take place outside the game such as in Discord, it's out of SE's hands.