But I'd say we don't have any example neither: regimes from your history books weren't "communism" we find in your philosophy books. You can see it if you read both carefully enough.

(and again, I'm not stating communism can work, because we don't know that).

But even if we assume both "communisms" are the same: you are saying "Communism has failed N times, therefore it will always fail". You don't know that (though I would admit it's quite solid evidence in this case)

We don't know. And I'm not arguing for or against communism here neither.