Depending on the configuration of the portlet instance and on your own permissions, you might be able to add a comment about a Blog post. For details, review "To post a comment," below. Note that if you have permission to comment, then you also have permission to delete your own comments.
Locate the Discussion area of the post on which you want to comment:
Display the full text of the post, either in the Blog portlet instance hosting the item or in the My Subscriptions version of the portlet.
Scoll down. The Discussion area is at the bottom of the page. If the post does not contain a Discussion area, that means that the author did not enable commenting for this post.
If the Discussion area of the post includes a text box labeled Post a Comment, then you have permission to comment.

If this box is not displayed, you don't have permission to comment, and you shouldn't continue with these steps.
Enter your comments in the text box.
Click Save.
+ To delete a comment you posted
If you have not already done so, locate the Discussion area of the post that contains the comment you want to delete:
Display the full text of the post, either in the portlet instance hosting the item or in the My Subscriptions version of the portlet.
Scoll down. The Discussion area is at the bottom of the page.
Locate the comment you want to delete. Click the corresponding trash barrel icon.

The system generates a dialog asking if you're sure you want to delete the post.
Click OK.
The system removes the comment.