It doesn't matter if it is an accident, you are still breaking a rule which means you should be punished for the action that you are breaking. You would know if your alt is banned, because if you have an alt account you would probably know if it was muted/banned.I mean, that's stupid that you can ban evade or mute evade, the staff can just ipmute you temporary or ipban you temporary...
First, you might not realize you're temp banned on your alt or main and you play on the other account, which counts as ban evading (even if you didn't mean to), and that will end in a devastating blacklist.
Second, when you accidently type something in chat with your alt (when you are perm muted / temp muted on main), it can end as a ban / perm mute, which is annoying.