JComments is a Joomla component that manages the comments. With this component, people can write comments on articles. They can also respond to previous comments.
Today, the plugin «FG Joomla to WordPress Premium» is compatible with the JComments component as a module. You can now migrate all your Joomla comments to WordPress. It imports all the comments data: the username, his Web site, his IP, the title and the body of the comment and the comment date. It also manages the nested comments.
You can purchase this module at: https://www.fredericgilles.net/fg-joomla-to-wordpress/jcomments/
Note: This module needs the plugin «FG Joomla to WordPress Premium» to work.