Through a meditation course I got from an app on my phone, I've been learning some communication skills. To summarize:
Be fully present with the person you are with.
Be very clear about what your needs are, and very attentive to what the other person wants or needs.
Your aim is to understand what the person is saying. You can ask for clarification. "So what you are saying is that...?" You want to show the greatest degree of empathy.
You want the other person to understand what you are saying too. You can ask them what it is they have understood from what you said, and clarify in turn. You want to come out of the meeting with a plan mutually agreed upon.
In giving feedback on student papers, I have attempted to do so from a place of great compassion and empathy. So I can say: "What I want you do in the revision of the paper is this: expand here; add signposting*; make all paragraphs at least 4 sentences long; clarify this or that idea." Substantively, my critique is the same as it would be using my older style of communication. It is not even a matter of being tactful, as I used to think. Being tactful is dressing up something negative in sweeter terms. Being compassionate is trying to see if from the other person's point of view.
*I don't like signposting, as you know, but I think certain students need it in order to clarify for themselves the shape of an argument. You can also go back and reduce it to the bare minimum.