You can choose who can comment on articles and who can view those comments. The two main groups are everyone and only logged in readers and users.
Restrict commenters sets who can physically comment on your articles. When checked, only users and readers who are logged in to your knowledge base are allowed to leave comments. Readers or users who are not logged in won't be able to submit comments.
Restrict visibility sets who can view comments. When this box is checked, only users and readers who are logged in to your knowledge base will be able to view comments. People not logged in will not see comments at all.