That is a good idea.
What would you suggest?
This is just me personally, but whether in writing or in person, I always try to "sandwich" a suggestion in between positive feedback.
For example: "You really expressed some important ideas here, and I'm really glad you took the time to tell us what was on your heart.
If I could, may I offer a suggestion? You might want to break your writing into a few more paragraphs, so that each thought is given the importance it deserves.
You've raised an excellent topic here and separating your thoughts a little helps us understand every point that you're trying to make. We want to make sure we're not missing anything."
I try to start out with a positive acknowledgement, turn the "correction" into a suggestion rather than a mandate or criticism, and then end with another positive affirmation.
This way, the receiver hears something positive at both the beginning and end, and hopefully walks away with a feeling of validation that motivates them to not only keep on sharing, but also consider utilizing the suggestions that were given.
This is just my own point of view and something I've learned to do after lots of trial and error, mostly error.
Thanks for asking, spunkycat--it was a great question.