They are replying to their multiple accounts with good ID but the moderator is banning the good accounts after seeing the replies of the multiple accounts which is causing loss to the good accounts.
Proof?
Moderator wouldn't ban a multiples accounts if they're not breaking strict rules (plagiarism/ban evaders), it's allowed to use multiple accounts as long as you not use for bad stuffs.
Seems you're talking about
work(signature campaign or bounties) when an alt accounts joined in many campaign, well if they're not using 2 or more accounts to join in same campaign it's allowed. If 2 or more accounts join in same campaign, you can report them and they will got removed.