Listing with JSON or plain HTML
First of all, there's a problem with the HTML approach you have:


That's risky (XSS most of the time)
Do you expect them to be web developers? I can be a gamer/reviewer with zero HTML knowledge.
We're writing a review, we should only write reviews, not HTML. Leave HTML to the developers.




Now, as you said, you can do JSON, and your other approach seems to be right:

Form

&lt;form&gt;
  &lt;h3&gt;Advantages&lt;/h3&gt;
  &lt;button&gt;Add&lt;/button&gt; // get nextAll advantages, find the last and append after
  &lt;input type="text" name="advantages[]" /&gt;
  &lt;input type="text" name="advantages[]" /&gt;
  &lt;input type="text" name="advantages[]" /&gt;

  &lt;h3&gt;Disadvantages&lt;/h3&gt;
  &lt;button&gt;Add&lt;/button&gt; // get nextAll disadvantages, find the last and append after
  &lt;input type="text" name="disadvantages[]" /&gt;
  &lt;input type="text" name="disadvantages[]" /&gt;
  &lt;input type="text" name="disadvantages[]" /&gt;
&lt;/form&gt;


Data structure to server

{
  advantages : ['foo','bar','baz'],
  disadvantages : ['foo','bar','baz']
}