You keep repeating this but as somebody from former Warsaw Pact country let me tell you there was a real caste system during communism. Party members were basically royalty. And the ruling caste (top, most loyal apparatchiks) were just like Louis XIV, having completely unlimited powers over other people.
The existence of castes - social classes - is in direct contrast with the definition of communism, which seeks a classless society.
Yes but it is not in contrast with every implementation of communism in human history.