How do I access the loaded comment object?
It is better to use kint() function of the devel module for debugging entities because you will get also a list of available public methods.

You cannot get all comment fields values by looping them as different fields have different array result structure. 

Using $comment = \Drupal::entityTypeManager()-&gt;getStorage('comment')-&gt;load($commentID) you get full comment object.

$comment-&gt;get('comment_body)-&gt;value you get comment body value as it uses some text format (eg. full html). 

You also can covert comment object to array $comment = $comment-&gt;toArray().