Since RSBlog! revision 2, you can import Joomla! content into your RSBlog! Posts area, thus transforming a plain article into a blog post, and also import the comments related to the posts into the commenting system set in RSBlog! > Configuration > "Comments Integration".
In order to achieve this you will have to install the RSBlog! - Joomla articles import plugin (available in the View my downloads area). To install it just head to Extensions > Install / Uninstall > browse the plugin and click Upload and Install.
After the installation, the import option will be available here: Components > RSBlog! > Import. You need to simply select the sections and categories and whether or not to import the existing comments.
The comments will be imported only if these are made by the following commenting systems: RSComments!, JoomComment, JComments.
