Now I’ve said not to be too harsh on writers when editing their work—well I have another piece of advice on the subject. Don’t be too soft on them either.
When an editor makes comments that are unclear about whether something is or is not incorrect, it not only leaves the writer wondering what they should do, but it will also hurt your reputation as an editor. Don’t let multiple comments start off with, “I think…” or “I’m not sure but maybe….” Take the time to look up the answer and declare with conviction that, “you need to change this to that.”
However, I’m just talking about technical mistakes they’ve made. You need to tell them to correct definite errors. There are also other comments that are more suggestions rather than pointing out errors. I often start out my suggestion comments like so: “Consider…” or “Would it read better like this?” That way, they know that these comments are my opinions. Sometimes I even insert in those comments, “this is just my opinion,” just to make sure they know that it’s not mandatory to change it to my wording.
Often times, if you are too soft on a writer’s work, they’ll not regard you as being a helpful editor. If they needed a morale boost with their writing, they would have taken their story to their mom to read. Give them compliments, show where their writing really excels and why, but also don’t forget that the main reason they are coming to you is for you to point out any disastrous discrepancies and to advise them on how to fix it. That comes first, pats on the back come second.
I’m don’t know how much feedback Stephenie Meyer received and took to heart on her Twilight series; but if it was minimal, there could have been fewer people bashing her work today if she had relied on hard editors that weren't afraid to say, "this character just does not work, and here's why".