How about altering how the Markdown would be rendered?

E.g., the previously mentioned input:

   [Check this cool similar new app out HN](http:/not.suspicious.com/nor/has/tracking)

Could be rendered as:

  <a class="link-display" href="http:/not.suspicious.com/nor/has/tracking">Check this cool similar new app out HN</a>
  <span class="link-content">[not.suspicious.com]</span>
  
  .link-display {
    /* Whatever styling you want for the link itself. */
    font-weight: bold;
  }
  
  .link-content {
    /* A more in-your-face helper that shows at least the domain. */
    font-style: italic;
    opacity: 0.5;
  }

Example: https://jsfiddle.net/upb7o0zm/

Copy-paste-friendly version:

    <a class="link-display" data-host="not.suspicious.com" href="http://not.suspicious.com/nor/has/tracking">Check this cool similar new app out HN</a>

    .link-display:after {
        content: " [" attr(data-host) "]";
    }

I'm not sure if the markdown spec mandate what the output should be, but I indeed love you idea!

That doesn't work on touchscreens.

Edit: Commenters say long-pressing reveals a URL without opening it in mobile browsers, which is nice to know. I only have experience with using regular desktop FF on my (Linux) phone, which doesn't support such a thing AFAICT.

Worked fine on mine (chrome on Android): touch and hold and wait for pop up. If the link in the upper right is cut short with an ellipsis, touching the link will expand it, just like ellipsis shortened alt texts.

no, but at least here on Fx mobile, i can long-tap and see where it's going.

Depends on the device and software. At least on my phone's Firefox browser a long-press of a link will bring up a menu that includes the URL (though it can run into space constraints for long URLs).

On iOS, that loads the page in a pop-over window.