How can I transfer node and comment records from Drupal 6 to Drupal 7?
You could look into using the Migrate module. Although I haven't used it myself, I know that many have been using it to move content from a Drupal 6 website into a Drupal 7 website. Be aware that it is an advanced module that has no UI (that I'm aware of). It integrates with Drush and allows you to create migration scripts and run them from the command line.