If you are like me you probably have searched for clues to and found little... particularly when confronted by the errors as you unravel how this works.  Okay a slight exaggeration, there are snipets of info that people have solved this annoying issue in  making comments work in Drupal 8 REST services. The lack of collective information in resolving issues has meant hours of debugging and working through core code to understand what is actually happening.  If you want to...

In Drupal 8.x hiding the subject line is a quick task. In the admin area of your site go to structure > comment types > {comment type} > manage form display and the URL will be like https://domain.com/admin/structure/comment/manage/{comment}/form-display.  I have put the type in braces as you might have several comment types.  If you only have the default Drupal setting, then use default comments and the path will...