I simply said it differently by applying it to pronouns in general. I wrote the comment because wanted to associate your way of explaining judicious use of referents with what I had already learned and, unfortunately, forgotten.

The point was clear, though. Never assume that the reader knows what you’re talking about. Pronouns are dangerous for this reason, even though the pronouns useful and necessary.

An extreme example of ambiguous pronouns would be saying that “Jack and his younger brother Jim went to an arcade. Naturally, he had a lot of fun.”

Um, which one had a lot of fun?

Of course, it is easy to spot obscure pronoun usage when the sentences are right next to each other. Larger paragraphs hold a lot of different subjects, and even if the author knows which pronoun goes with each subject, the reader shouldn’t need to work as hard as the author. If there is only one “he” being talked about, for instance, if Jack brought his sister along, then the pronouns could be used more often.