Works just fine even after 8 yeas from the last update. I’m amazed that there was no easy way to change the comment relations with the native functionality of WordPress. Often the visitor doesn’t care where to comment and create mess on your site. Or even you site manager sometimes mistakenly does that. I tried different plugins that appeared at top of search results but none of them worked (can’t believe) but this one does. I had to login to an old web site that installed this one to find the plugin that works. By the way, this plugin doesn’t seem to appear in the search results of the wordpres.org plugin listing. If you go to Dashboard -> Plugins -> Add New and type the name of this plugin. It doesn’t hit anything. Even changing the search type to Author and type Sergey Biryukov, it doesn’t find it either. I don’t understand why wordpress.org hides this well functioning plugin. The UI is just minimum and simple and does the job.

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