For each review cycle you can choose if Reviewers can see each other's comments. Developers and Uploaders can always see all comments.
If a cycle was set as not shared then Reviewers of later cycles will not be able to see those previous comments.
Some teams use this for internal/external reviews.
- They set the first cycle as NOT shared and let their internal team make comments. As Developers they can still each other's comments.
- Then the create a new cycle for external Reviewers and turn on comment sharing. The new Reviewers will not be able to see comment from the first cycle.
Technically you can update this setting at anytime, but in practice you may want to avoid changing it late in the cycle. It may confuse Reviewers if the other comments show/hide during the cycle.
Note: Once you create a new cycle you cannot go back and change the sharing option of the older cycle(s). So if sharing was turned on for cycle one when you upload a new cycle; everyone in cycle two will be able to see those comments and you will not be able to go back and change it.
This option is set on the Course Details page: