Announcements - Close for Comments
When you create an announcement, you can allow comments on that announcement by selecting the Allow Participants to Comment checkbox in the announcement options. Additionally, if an announcement allows users to comment, you can require students to reply to the announcement before seeing other replies.
You can also allow or disallow comments after an announcement is posted.
Note: If the Allow Participants to Comment checkbox does not display or does not remain checked, allowing comments on announcements may be disabled for the entire course in Course Settings.
For more information, click on this link to the Canvas Community help guide.
Watch this video for step-by-step coverage of this topic: