I am currently looking into general ways of preventing this type of hack. Thanks to some player tips I believe I know how it is done, so the task is to work out the best way to prevent it so that other similar hacks will also be prevented.
To be clear, we are not running some kind of personal vendetta against individual players. All we want is a non-toxic and fun environment for our whole player base. Hacking is the worst offence, because hacks when shared will damage the game experience for all players - it has happened in this game before.
If a banned player wants to create a new account and play without insulting or hacking then I consider loss of their original accounts sufficient and do not pursue them further through the data.