Post Comments to Articles
The knowledge base is a space for exchanging information and sharing ideas. One of the key components that create this sense of conversation is the comments section.
Comments let you and other members of your team engage with the author and discuss the content on the page. You can use comments to ask and answer questions and provide supplemental information.
To add a comment to an article, just enter your comment text and click the Submit button. The controls in the toolbar let you attach files, format your comment text, or embed files, images, and other documents.

Visibility for Comments
Any comment posted to an article inherits the current visibility setting from the issue.
When you restrict the visibility of an article, the default visibility setting for new comments is set to Same as article.
You can restrict the visibility of a comment to a subset of the users for whom the article is visible. For example, if the article is visible to article readers, you can restrict the visibility of a comment to group A or any other users who have permission to read articles in the project. To learn more about the visibility options for articles, see Manage Article Access.
The setting for restricting the visibility of an article comment is located just below the input field for a new comment. To update this setting, select or deselect users, groups, and teams. The selection is applied automatically.

Keep in mind that if you set the visibility for a comment to a user or group for which the article itself is not visible, the user and members of this group still cannot read the comment.