Do try, in fact, remove; any copies of this post. If you have done cross-posting, you might get yourself in trouble with the forum. Stick to a single post about this matter in a single place. Maybe here or in Gambling Discussion if this is a gambling site. Otherwise service discussion i think. Cross posting not only does not make your message more read, it might in fact trigger mod reaction and you will get the opposite effect. Don't say sorry, just don't do it, you already know its bad.
He doesn't have to remove the post, he just needs to give a source if possible.
Though in this case, he already prefaced his post saying that he posted this on multiple forums, I think it's clear he's not plagiarizing.
Now, OP, you really need to reach out in as many public channels as possible. I hope you've already contacted them in Twitter as well? Maybe even reddit?
If you're telling the truth, it's plain and simple theft they're committing.