Sorry we didn't get back to you previously, @abelinuxmx! We know this is something people want. I've moved this thread to Features because it doesn't look like we're tracking this there. Include server log in data download from Central - #3 by Florian_May has some mention of it.
It would be helpful to understand what you would like to do with this and what format it would be helpful to have it in.
You can currently grab all of the comments for a specific submission via the API: https://odkcentral.docs.apiary.io/#reference/submissions/comments/listing-comments This means you could consider creating your own export document from an external script.