These contexts don't change the idea in rule 1, but they do change the definition of what is "necessary". There are words that "dilute" a message and are not necessary to convey the literal meaning. But usually we don't want just the literal meaning of things, we want a certain level of dilution. Without it, prose can be clear and specific, but at the same time becomes dense and unreadable. Lots of academic writing is like that.

There are words that are necessary for the _overall effect_, even if not necessary for the literal communication goal of a set of words.