It is descriptive rather than evaluative. Especially at the beginning of a post-observation conversation, try to avoid major global evaluations. If someone is very uncomfortable, be reassuring by starting with some of the strengths you saw. It is specific rather than general.
More specificity usually means more credibility for the feedback.
Also, discipline-specific knowledge is often very highly valued. Sometimes you may want to show the TA or instructor your notes if there isn't anything evaluative in them. It is focused on behavior rather than on the person. Ideally, cite the impact of instructor behavior on student learning. You may also want to ask questions during the post-observation conversation about how the person feels about certain behaviors if they appear uncomfortable in some way.