NOTICE: This is solely NOT a WordPress Question, but related to WordPress Migration and Export-Import.

I started blogging in WordPress and then shifted my blog to a self-hosted site. But even after that, I din't shut down my blog for some internal reasons. Though I stopped updating the blog, users are still commenting there. But after a long time, I now determined to shut down the site. But before that, I want to import some of the new comments, those posted after the migration.

Suppose, post#5 had 3 comments, when I migrated, now it has 5 comments — so, 2 new comments are in post#5.

As because I have to Export .xml data from the site, and the .xml contains all the post comments etc. in it. So, I've to find out a way that only import and add, but doesn't duplicate and/or delete and/or overwrite any of my site's present post content or comments or any other settings.

Is that really possible?

EDIT

What I got so far is the .xml, and I got that the comment resides under <wp:comment> under each <item> with the $post_id and others:

<item>
 <wp:post_id>$post_id</wp:post_id>
 <wp:comment>$comment</wp:comment>
</item>

I've actually no idea about how to proceed with WordPress .xml data file.