As a professional author and editor, I deal with feedback and criticism all the time - both giving and receiving, and I agree with most of your points about how to provide feedback.
Being positive in tone and presentation is certainly one of the best approaches in my experience. There's a reason it's called "constructive" criticism. Using an opportunity to give feedback and just running someone down is never going to result in the person receiving the feedback taking it to heart.
This is of course more of an issue with creative types than those in the business world - especially when it comes to fine art and literature. Artists are notoriously thin-skinned, and unless you ensure that you provide negative feedback in a positive way, creative content creators can get very upset - and then the feedback doesn't have the desired effect.
Glad I read through the comments and found this post. I think you're right that writers and artists can be sensitive to criticism but, at the same, if someone has engaged with your work closely enough to be able to criticise it, then that's a pretty good start. It shows that there's something there that the reader thinks it's worth drawing out, and if they are prepared to spend their time making your work better then that's a great compliment.
Anyway, I'm excited about what your skills as an editor and an author can bring to the fiction community on Steemit :)
I think you've hit it right on the head there. The idea is communicating to someone you're giving feedback to is that you're invested in their success enough to want to improve it, and make it the best it can be, helps people - especially creative types - understand that even if you're telling them ways they can improve, it's coming from a positive frame of reference.
And thank you! I'm doing my best to offer feedback where it's wanted and just general help in many of my posts.