I wish code.org introduced comments in the program early on. Some the example code and starter code has comments; however, comments are not a option for the students to use until some of the later lessons. To encourage commenting in the students work, I would like to see this option opened up to the students with the beginning of Unit 5.
I agree that getting students in the habit of documenting their code early is important. Comments were introduced in Lesson 8 of Unit 3 so it probably wouldn’t be unreasonable to have the comments block available as early as possible in Unit 5. Although it is a feature request, you can submit it using the ‘report bug’ feature on Applab’s menu in the top right corner.
Until then, students can be encouraged to add comments in text mode using //.