Found this user replying to this own post with his alt. For what purpose? Cheating signature quota. It's obvious that this user struggling with his post count quota. And for the sake of it he will reply to his own post. Not just that cheating of forum translation, contest and giving merit to own his alt account
There is no rule to ban account because they are alts, quote each other.
If you think they are alts, cheat in a campaign, you can report it to the campaign manager and the manager will decide. You already opened an accusation thread in Reputation board, that's enough.
These accounts if they are alts, will not be banned because of what you reported. They will only be banned if you can find proof that they made ban evasion.
25. Ban evasion (using or creating accounts while one of your accounts is banned) is not allowed.[e]