Migration to Self Hosting Blog – Some comments Lost

Hi,
I had the free wordpress blog happyandharried.wordpress.com and I moved to a self hosted one happyandharried.com
I moved my data using export-import. I created a new admin user for the new self hosted blog. I imported all posts from the wordpress.com blog under the new user’s name. But I see that some posts are missing their comments section now. The original comments have been imported, I can verify that when I go to Comments page from my dashboard. The “link” between posts and their comments seem to be broken.
My question is, whether this is because there are two different users now? Can I make my old user as admin for the new blog?
Will this bring all the comments back? Can a blog have multiple admins?
Or is it some other issue during migration? How do I solve this?

Thanks in advance for your help,
Anjana.