I am reporting https://www.drupal.org/documentation/modules/block_content to moderators because:
It needs to be deleted, given that it is an almost perfect duplicate of https://www.drupal.org/node/2112591 in the Drupal core module section.
Also, the ‘Custom Block’ module is not a contrib module, but rather a D8 core module,
so this page in the ‘contrig’ section is the one page of the two pages that should disappear.
Thank you kindly for you attention to this matter.