The dictatorship of the proletariat is not communism. Not even for Marx. It is the state before communism, in which the proletariat makes changes in society so that communism may take place.
Nice try, but I explicitly stated I was talking about Marxist-style socialism, which is what 'communism' has come to mean. I almost never see people talk about "real" Marxist communism anyway.
You explicitly said "Communism in the formal sense". You were wrong with that.
Most ideologies and political or economic ideas have had their names subverted to mean something different by opponents (democracy, republicanism, communism, anarchism, capitalism...). That doesn't mean that if you speak in the "formal sense" you can decide to use whatever meaning you prefer.