To reproduce this issue:

1. As a logged-on user go to your profile and click "Blog entries".
2. If there's no blog entry yet, create a new one.
3. Back on the Blog entries page, click the comments link to expand the comments and show the comment text area.
4. Check that the comment text area shows a placeholder text "Add a comment..."
5. Click again on the comments link to hide the comments and the text area.
6. Click again on the comments link to expand the comments and the text area. Notice that the "Add a comment..." placeholder text is not being shown.