A comment can concentrate on an entire lecture series or on a single issue, argument or concept. It can be a new insight, an argument, a counter-argument or an opinion. A comment can also consist of matters/concepts/theories not discussed during the lecture, but which are related to the topic. It is crucial to concentrate on central ideas, not small details.
A good comment is critical and complementary. It approaches a theme critically, argues and gives reasons for opinions, arguments, problems or solutions. A comment can apply ideas or arguments from different resources. You can use books, articles or the Internet for gathering material for your work. All comments, use of references and concrete examples are advances.
At first you may find writing a Lecture Diary difficult. Writing is a skill, which cannot be learned in one night. It takes time and effort. It is very important to find a regular time slot to dedicate to the Learning Diary. It makes writing easier and you get better results than when writing all during one sitting.