Theme reply comments differently from node comments (Drupal 7)

Question

I am using Drupal 7. I have a question/answer website, I want to theme reply comments differently from node comments. How can I apply a different css theme to differentiate node comments from comment replies? I checked the css class and both node comments and comment replies have the same css class. So how do I add different css class to comment replies and theme them differently?

Clarification: My question is just about theming comment replies differently, like removing borders around them or adding background to all comment replies, while node comments (answers) remain same.

Answer 1

You will have to use the surrounding classes to target the direct comments. Consider a site with the following structure (this is actually based on drupal.org):

...
<div class="content">
  <div id="node-01" class="node node-forum clearfix">
    ... Node content ...
  </div>
  <section class="comments comment-wrapper">
    <h2 class="title">Comments</h2>  
    <a id="comment-7635897"></a>

    <div class="comment clearfix">
      ... Comment content ... 
    </div>

    <div class="indented"><a id="comment-7728095"></a>
      <div class="comment comment-by-node-author clearfix">
        ... Comment reply ...
      </div>
    </div>
  </section>
</div>
...

Node comments can be targeted with the CSS selector .comment-wrapper > .comment. (only target first level childs).

Replies can be targeted with .indented .comment (target all level childs of indented comments).

So have a look at your site's structure and try a similar approach.