Alter comment links in blog teaser in drupal 7
If I were you I'd hide the span content in CSS and add a tag for my background image like this:

Template:

&lt;li&gt;
    &lt;span class="comment-hidden"&gt;&lt;?php print ($comment_count); ?&gt;&lt;/span&gt;
    &lt;span class="comment-count"&gt;&lt;/span&gt;
    &lt;?php print render($content['links']['comment']); ?&gt;
&lt;/li&gt;


CSS:

.submitted ul li span.comment-count { 
  width: 16px; // or whatever
  height: 16px;
  background: url("../images/blue-bubble.png") 0px 2px no-repeat;
  background-size: 100% 96%; 
  padding: 0px 5px 5px 5px; 
}

.submitted ul li span.comment-hidden { 
  display: none;
}