Here's the real life example:

  1. Basic Drupal installation with only the Basic page and Article node types.
  2. A view of certain Basic page nodes.
  3. An accidental creation of an article instead of a page.
  4. Use node_convert to convert the article to a basic page (discard image and tags).

After the conversion noticed that the converted node was the only one to have a "add comment" link besides a "read more" like all the other nodes of the same type. I had to edit the converted node and manually set the comments to "closed".

So there should be an option during the step that asks what fields should be converted to about comments as well.