I have quite a lengthy WP based blog that I've been using for a while. My question is what would happen to the comments received on posts and archives, if I were to migrate to ghost.
Are word-press users allowed to post comments on ghost blog pages?
If you are using the Ghost exporter plugin, it will only take your posts. The best way to get your comments is to first migrate them to Disqus, and then use the Disqus comment system in your Ghost blog.
Here is a breakdown on how to do that (link)
Hope that helps!