From the comment page, click on Change status in the status column, the following window will pop up:
Comment "status" is an attribute used to keep track of a comment’s life-cycle. Can be: New (starting status of new comment), Closed or Resolved. To modify the status of a comment, choose the desired statuses from the "Next status" and the "Next sub-status" drop-down menus and click on "Submit".
Severity indicates the importance of the comment, and priority indicates can be: Low, Medium or High.