Say “this paragraph is confusing,” not “you’re a bad writer.” One helps them fix it. The other just makes them quit.

Feedback aimed at the work gives someone a next step; feedback aimed at the person gives them an identity. Once criticism becomes about capability, the only available responses are defence or quitting, and most people quit quietly. The same observation can be delivered either way, so the choice is yours every time. Specificity is what makes it usable.

Point at a line, a paragraph, or a decision, and say what happened when you read it. Add what you would try, tentatively, and leave the choice with them. Keep the word you out of the sentence wherever you can.