You are allowed to create an account to ask if you can be unbanned. However, you can only post inside Meta and only for this purposes. Everything else will be considered as ban evasion.
If any accounts that he previously used have been banned, then this could be considered as ban evasion as he has posted outside of meta.
Hope they get back to me soon.
If you don't get a response in a reasonable time, then you should take that as a no to your request/question.