Hi @absurdo,
I apologize, you’re right, by mistake I answered you what I wanted to reply to another user, sorry for the confusion.
About exporting all your comments, it’s weird that it appears with 0 comments.
Are you using the WP tool for exporting content in:
Dashboard > Tools > Export > All Content (This will contain all of your posts, pages, comments, custom fields, terms, navigation menus, and custom posts.)
If it’s the case, I recommend you to click there and to check the file generated to see if there are comments there.
If there are comments, then you’ll know that the issue is related to the import process.
If there are no comments, maybe the problem is related with the server’s config option in php.ini: “max execution time” or “time out”, that you’d like to increase in case that time is too low and because of that, WordPress is not exporting all the content, so you could be getting a not complete XML file without the comments.
Does this make sense? Let us know!