We don't just ban for using the $upvote on another account, we actually don't mind someone helping out another person.
What tends to cause it is when we suspect that both accounts are suspected of being the same person. We do in fact have hundreds of accounts that try this. It's hard to be sure about who is doing it and who is just helping someone out. We do occasionally get it wrong and we do have methods for verifying if there are 2 separate people.
We have a MSP Probation Discord server you can join to talk to us and we can start the process there for verification.
We have several things we look at to determine a connection between accounts, and while I haven't looked at your specific ban yet, we are always willing to try and verify if we got it wrong.