In one example, students found "nothing to complain about." In this case, the teacher explained to them that they should write "has no solution". This procedure does not seem completely correct to me, I would personally explain to students (or state as interesting) that the expression itself is a solution, because I can "rebuke 1" and copy the expression, so it is not true that nothing could be rebuked. However, the teacher apparently did not want to "confuse the students" and apparently draws on her experience, which forced me to think about the adequacy of the interpretation and curriculum.
This procedure does not seem completely correct to me, I would personally explain to students (or state as interesting) that the expression itself is a solution, because I can "rebuke 1" and copy the expression, so it is not true that nothing could be rebuked.