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Therefore, if I go to the Italian board, and write new information, reply to a topic, or share something relevant, I am not translating content but creating content.
Am I really wrong with this reasoning?

It is true that afterwards everything needs to be interpreted by each one. But, I think I'm not very wrong in this line of reasoning.
As for the specific Italian board, of course, I am not the moderator here, but I guess it is ok, provided that the translation is intelligible (but this is usually the case if translating from English) and, as you said, you are posting original content and not spamming ANN threads or so.
But again, it is really dependent on the relevant mod for other boards, and in my honest opinion, it is not a hill to die for. I think I found a decent compromise.