Discussions are the only place that learners can see each other in a course (and then only if they choose to participate).
If for any reason you need to disable the discussion feature, you can adjust this per cohort or per entire course (affects all associated cohorts).
To disable discussions course-wide
To turn off discussions for a course, open the "Course Settings." Go to "More Settings" and toggle "Enable discussion?" to the off position.
To disable discussions for one cohort
To turn off discussions for a single cohort, open the cohort settings (called "Change access" on the course drop down menu), and toggle "Enable discussion?" to the off position.
Toggling discussions off will hide any existing discussions.
You can toggle discussions back on anytime.