Don't worry too much about MS Word griping about your use of passive tense. It's only a computer algorithm. They base it on the notion that too much use of passive verbs takes some of the punch out of your writing. I agree--to a point.
A passive statement removes a lot of the responsibility for action from the subject of the sentence. You could write "Mistakes were made," or "The woman was criticized." The first example assigns absolutely no responsibility for the mistakes; the second doesn't tell us too much about who actually criticized the woman. The previous examples are quite common in both bureaucratic and academic writing. They have the effect of separating the reader and the writer from human causation Some people I have worked for looked at passive writing as sophisticated and lofty. (I disagreed.) If that's the goal, then passive writing can be successful--but it doesn't make it good.
So, as a professional freelance writer, I avoid excessive use of passive voice. If use of the passive conveys my meaning in a way that fits in with everything else I wrote in the piece, I'll use it sparingly.
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