The UI is created by javascript and does not include any of the standard aria roles or attributes.

All links acting as buttons should have the role="button" attribute and the regions where comments are added/deleted dynamically need aria-live="polite".

The comments(X) link should have aria-controls (and the div should have aria-expanded).

The focus should be set to the header after deleting a comment.
The focus should be set to the new comment after adding a comment.