Best Way to Add UnEditable HTML to Posts

Is there a way to make it so that the user cannot delete certain
things inside posts content?

You need…

  1. A shortcode that will generate the content. This will let your users
    provide input but the markup can be rigidly controlled.
  2. Or a custom meta field. The markup around this can also be rigidly
    controlled, but to a lesser extent, or in a different way.
  3. Or you need to write the markup into the templates.

I can’t tell you exactly which you need. I’m not sure. I think the shortcode, or a group of shortcodes, might do what you need.