Render published content or comments on new created content using a link
You can use an Entity Reference field.  In Drupal, most of the &quot;content&quot; that you see, including nodes and comments, are entities.
Entities can be linked to each other with an Entity Reference field.
Here's a tutorial video.
One challenge when working with Entity Reference is that each field can only reference one type of entity-- so you can have an Entity Reference field for nodes, or for comments, but not both at the same time; to have both, you need two fields.
Out of the box, Entity Reference can be configured to select the content by autocomplete or by a select list, which can be the output of a view you have customized, so it's quite flexible.