CodingFabian

Because WPML creates posts and pages for each language, comments from one do not appear on the other. 
This plugin merges comments from all WPML translations of the posts and pages, so that they all are displayed on each other. 
Comments are internally still attached to the post or page they were made on.
It uses the <code>get_comments()</code> api call, which in some circumstances might not return all posts.

WPML comment merging

This plugin merges comments from all WPML translations of the posts and pages, so that they all are displayed on each other.

Amir Helzer

David Garcia Watkins

Pierre Sylvestre

This plugin can either cleanup the qTranslate X meta-HTML tags from your site and leave just one ‘clean’ language, or migrate all languages to WPML’s format.
Very important: This plugin will modify the entire content of your database. You must backup your database before attempting to use it.
For complete documentation, please refer to the <a href="https://wpml.org/documentation/related-projects/qtranslate-importer/?utm_source=plugin&utm_medium=gui&utm_campaign=qtranslate" rel="nofollow ugc">qTranslate uninstall and WPML importer documentation</a>.
<h4>qTranslate X uninstall and cleanup mode</h4>
Must-read: All the issues mentioned in the reviews are solved. We are happy to announce the reintroduction of the clean-up mode with plugin version 2.0
This mode is intended if you just want to keep one language in your site and you want to clean up the language meta-tags that qTranslate added. For this mode, you don’t need WPML.
Instructions:
<ol>
<li>Save all qTranslate X settings</li>
<li>Go to the Plugins admin page and de-activate qTranslate X</li>
<li>Install & activate QT Importer</li>
<li>Go to Options -> QT Importer, select language to keep and click Start. </li>
</ol>
<h4>Migrate all languages from qTranslate X to WPML</h4>
In this mode, the QT import plugin will convert the language information from qTranslate’s language tags format to WPML’s post-per-language format. For this to work, you must have <a href="http://wpml.org" rel="nofollow ugc">WPML</a> active in the site (but not necessarily configured).
Instructions:
<ol>
<li>Save all qTranslate settings</li>
<li>Go to the Plugins admin page and de-activate qTranslate X</li>
<li>Have WPML activated, but not yet configured (just activated)</li>
<li>Install & activate QT Importer</li>
<li>Go to Options -> QT Importer and click Start</li>
<li>Add redirects from old URLs to new URLs</li>
</ol>
The import runs in small batches so it doesn’t have timeout issues with large databases. You can run it on sites of any size.
During the import process, the plugin generates a set of URL redirect rules. These rules tell visitors and search engines that the URLs in your site have changed (from qTranslate’s format to WPML’s format). When the import completes, you’ll be able to export these rules either as rewrite directives for your .htaccess file or as a PHP file to add to the theme.
You can skip the redirect rules, but then, incoming links to internal pages may lead to 404 pages.
The import tool converts posts, meta data and taxonomy. We tried to take every possible scenario in mind, but there’s no alternative to manual testing. Please consider spending time reviewing the final result and possible doing some last touch-ups before relaunching the site with WPML.

qTranslate X Cleanup and WPML Import

Migrating my QTranslate site to WPML worked flawlessly and saved me a lot of time.

A real time saver

Allows a complete uninstall and cleanup of qTranslate X meta-tags or importing translations into WPML

WPML comment merging vs qTranslate X Cleanup and WPML Import