Sergey Biryukov

Adds parent comment ID meta box to a comment editing page. Use to make existing comments threaded.

Edit Parent Comment ID

Instead, I advise you to use this plugin Change Comment Parent



New alternative to this plug-in

Adds parent comment ID meta box to a comment editing page.

水野史土

This plugin shows post/page/category/tag/comment/media/user IDs on admin’s edit post/page/category/tag/comment/media/user pages. You can see the ID when you visit an edit post/page/category/tag/comment/media/user page. 
Since this plugin hooks on ‘edit’ link, only users with priviledges can see IDs. For example, a user of author role can see post IDs, while a user of subscriber role cannot.
You can find a brief description in Japanese on a book <a href="https://php4wordpress.calculator.jp/" rel="nofollow ugc">Introduction to PHP for WordPress Users.</a> (written in Japanese.)

ShowID for Post/Page/Category/Tag/Comment

This plugin shows post/page/category/tag/comment/media/user IDs on admin's edit post/page/category/tag/comment/media/user pages.

Edit Parent Comment ID vs ShowID for Post/Page/Category/Tag/Comment