A comment can be added to every question, also for the questions which could be corrected automatically. If a test consist only of autocorrecting questions, the correction mode need to be set to manual.
But also if the correction mode is manual, a manual correction in the assessment tool is not possible. no comments can be added, as no question item need to be corrected manually
--> if manual correction is selected in the test configuration, in the assessment tool a comment to every question can be added