Hi,
I've had a few requests recently asking how I achieved comment merging with Polylang on my site http://inredningsvis.se
I ended up having to make changes to a few different files. It was a while ago now so I don't really remember exactly what I did. However, I made a zip of the 2 plugins I used for this, as well as my functions.php You'll need to copy the last section of my functions.php to your functions.php Do NOT update to the latest version of polylang.
http://inredningsvis.se/polylang-comment-merge.zip
I can't offer any help or support beyond that. Try contacting the plugin author if you have further issues :) Good luck!
Hope that's useful for someone.
Jon