Well, okay, let's imagine for instance that Tether comes to the forum and opens its topic to share news and answer questions. They hire one representative after another and this goes on for some time. Then it's revealed anyhow that one of those guys they hired was a ban evader during he worked for Tether as their representative.
That's the opposite case, and I guess it can be handled on a per-case basis. What Royse777 was suggesting is that a banned user can continue posting using Tether's account. I don't think that's allows.
Or maybe Tether in this case should just be held liable for their employees' spam, and be banned forever. I wouldn't miss them.