The feedback a teacher gives to an essay question is not available to the student in the course - it is sent by mail to the student.
This is inconsistent with how Moodle shows feedback in other modules, and confusing.

Most teachers as well as students would think the student can see the graders feedback for essay questions in the Lesson module in the same way as they can in other moodle modules.

There is a plugin, https://moodle.org/plugins/block_lesson_essay_feedback, but this is searching for a maintainer.