Found in Version 1.55.2 Jul 6 2021 18:40 but may have been introduced earlier.
Forever bans can be bypassed when using a toon/an unbanned account after waiting a few hours offline from the chat. (approximately 4-8 hours) Note that no IP changes have occurred.
1. Go to a chat
2. Get banned forever
3. Leave the chat for a few hours (4-8 hours)
4. Go to the chat using incognito mode or after clearing cookies
5. Notice you can rejoin the chat like nothing happened.
<- Unbanned like nothing happened after waiting 4-8 hours offline from the chat.