How do I close a Discussion for comments?
To manually stop students from posting replies to discussion posts, use the close for comments link. You can also pin discussions to the closed for comments section on the discussion index page.
Note: You can automatically set your post to close for comments on a specific date by creating discussion availability dates.
Click the title of a discussion.
Close For Comments
Locate the Settings icon  and click the Close for Comments link.
Note: For Graded Discussions, the Close for Comments option will not appear until after the Discussion due date.
Re-Open for Comments
If you want to re-open your discussion, locate the Settings icon  and click the Open for Comments link to re-open the discussion for comments.