Caixa de comentários personalizada

-Primeiro faça o dowload do seu blog.
- Vamos em desing, editar HTML,
- Clicamos em expandir modelos de widget;
- Ctrl +f e procure por;

#comments h4 {
margin:1em 0;
font-weight: bold;
line-height: 1.4em;
text-transform:uppercase;
letter-spacing:.2em;
color: $sidebarcolor;
}
#comments-block {
margin:1em 0 1.5em;
line-height:1.6em;
}
#comments-block .comment-author {
margin:.5em 0;
}
#comments-block .comment-body {
margin:.25em 0 0;
}
#comments-block .comment-footer {
margin:-.25em 0 2em;
line-height: 1.4em;
text-transform:uppercase;
letter-spacing:.1em;
}
#comments-block .comment-body p {
margin:0 0 .75em;
}
.deleted-comment {
font-style:italic;
color:gray;
}

-Substitua por:
#comments h4 {
margin:0;
font-weight: bold;
line-height: 1.4em;
text-transform:uppercase;
letter-spacing:.2em;
color: #000;
}
#bg_commentblock {
width: 548px; /*tamanho da area externa dos comentarios*/
background: #ffffff;
float: left;
padding:20px;
margin:0 0 10px 0;
border:1px solid #C0C0C0;
}
#commentblock {
width: 510px; /*tamanho da area externa dos comentarios*/
background: #E8E8E8;
text-align:left;
padding: 20px 20px 10px 20px;
margin: 10px 0px 0px 0px;
border-top: 2px solid #333333;
border-bottom: 1px solid #333333;
}
#commentblock ol {
list-style-type: square;
margin: 0px 0px 0px 10px;
padding: 0px 0px 10px 0px;
}
.commentdate {
font-size: 12px;
padding-left: 0px;
}
#commentlist li p {
margin-bottom: 8px;
line-height: 20px;
padding: 0px;
}
.commentname {
color: #333333;
margin: 0px;
padding: 5px 5px 5px 0px;
}
.commentinfo{
clear: both;
}
.commenttext {
clear: both;
margin: 3px 0px 10px 0px;
padding: 20px 10px 5px 10px;
width: 490px;/*tamanho da area de comentarios*/
background: #FFFFFF url(http://lh4.ggpht.com/kangrohman/SMZb-VqQlYI/AAAAAAAAAOM/RpT6fNN3M88/commentgray_thumb%5B1%5D.gif?imgmax=800) no-repeat top left;
} /*cor do fundo combindo com cor da imagem*/
.commenttext-admin {
clear: both;
margin: 3px 0px 10px 0px;
padding: 20px 10px 5px 10px;
width: 490px;
background: #FFFFFF url(http://lh4.ggpht.com/kangrohman/SMZb-VqQlYI/AAAAAAAAAOM/RpT6fNN3M88/commentgray_thumb%5B1%5D.gif?imgmax=800) no-repeat top left;
}

Agora procure por:

<b:includable id='comments' var='post'> 
<div class='comments' id='comments'> 
<a name='comments'/> 
<b:if cond='data:post.allowComments'> 
<h4> 
<b:if cond='data:post.numComments == 1'> 
          1<data:commentLabel/>:
        <b:else/>
          <data:post.numComments/> <data:commentLabelPlural/>:
        </b:if>
      </h4>
      <b:if cond='data:post.commentPagingRequired'>
        <span class='paging-control-container'>
          <a expr:class='data:post.oldLinkClass' expr:href='data:post.oldestLinkUrl'><data:post.oldestLinkText/></a>
          &#160;
          <a expr:class='data:post.oldLinkClass' expr:href='data:post.olderLinkUrl'><data:post.olderLinkText/></a>
          &#160;
          <data:post.commentRangeText/>
          &#160;
          <a expr:class='data:post.newLinkClass' expr:href='data:post.newerLinkUrl'><data:post.newerLinkText/></a>
          &#160;
          <a expr:class='data:post.newLinkClass' expr:href='data:post.newestLinkUrl'><data:post.newestLinkText/></a>
        </span>
      </b:if>
      <dl id='comments-block'>
        <b:loop values='data:post.comments' var='comment'>
          <dt expr:class='&quot;comment-author &quot; + data:comment.authorClass' expr:id='data:comment.anchorName'>
            <a expr:name='data:comment.anchorName'/>
            <b:if cond='data:comment.authorUrl'>
              <a expr:href='data:comment.authorUrl' rel='nofollow'><data:comment.author/></a>
            <b:else/>
              <data:comment.author/>
            </b:if>
            <data:commentPostedByMsg/>
          </dt>
          <dd class='comment-body'>
            <b:if cond='data:comment.isDeleted'>
              <span class='deleted-comment'><data:comment.body/></span>
            <b:else/>
              <p><data:comment.body/></p>
            </b:if>
          </dd>
          <dd class='comment-footer'>
            <span class='comment-timestamp'>
              <a expr:href='data:comment.url' title='comment permalink'>
                <data:comment.timestamp/>
              </a>
              <b:include data='comment' name='commentDeleteIcon'/>
            </span>
          </dd>
        </b:loop>
      </dl>
      <b:if cond='data:post.commentPagingRequired'>
        <span class='paging-control-container'>
          <a expr:class='data:post.oldLinkClass' expr:href='data:post.oldestLinkUrl'>
            <data:post.oldestLinkText/>
          </a>
          <a expr:class='data:post.oldLinkClass' expr:href='data:post.olderLinkUrl'>
            <data:post.olderLinkText/>
          </a>
          &#160;
          <data:post.commentRangeText/>
          &#160;
          <a expr:class='data:post.newLinkClass' expr:href='data:post.newerLinkUrl'>
            <data:post.newerLinkText/>
          </a>
          <a expr:class='data:post.newLinkClass' expr:href='data:post.newestLinkUrl'>
            <data:post.newestLinkText/>
          </a>
        </span>
      </b:if>
      <p class='comment-footer'>
        <b:if cond='data:post.embedCommentForm'>
          <b:include data='post' name='comment-form'/>
        <b:else/>
          <b:if cond='data:post.allowComments'>
            <a expr:href='data:post.addCommentUrl' expr:onclick='data:post.addCommentOnclick'><data:postCommentMsg/></a>
          </b:if>
        </b:if>
      </p>
    </b:if>

Substitua por:
<b:includable id='comments' var='post'>
  <div class='comments' id='comments'>
    <a name='comments'/>
    <b:if cond='data:post.allowComments'>
<div id='bg_commentblock'>
<h4>
Comments :
   </h4>
   <div id='commentblock'><!--commentblock-->
<b:if cond='data:post.numComments == 1'>1
        <b:else/>
           <strong><data:post.numComments/> <data:commentLabelPlural/>  to &#8220; <data:post.title/> &#8221;</strong>
        </b:if>
      <dl class='commentlist'>
        <b:loop values='data:post.comments' var='comment'>
          <span><dt expr:class='&quot;comment-author &quot; + data:comment.authorClass' expr:id='data:comment.anchorName' style='display:inline'>
            <a expr:name='data:comment.anchorName'/>
            <b:if cond='data:comment.authorUrl'>
              <a expr:href='data:comment.authorUrl' rel='nofollow'><data:comment.author/></a>
            <b:else/>
              <data:comment.author/>
            </b:if>
            <data:commentPostedByMsg/>
          </dt> on &#160;<dd class='comment-footer' style='display:inline; margin:0px'>
            <span class='comment-timestamp'>
              <a expr:href='data:comment.url' title='comment permalink'>
                <data:comment.timestamp/>
              </a>
              <b:include data='comment' name='commentDeleteIcon'/>
            </span>
          </dd></span>
          <dd class='commenttext'>
            <b:if cond='data:comment.isDeleted'>
              <span class='deleted-comment'><data:comment.body/></span>
            <b:else/>
              <p><data:comment.body/></p>
            </b:if>
          </dd>
        </b:loop>
      </dl>
      <b:if cond='data:post.commentPagingRequired'>
        <span class='paging-control-container'>
          <a expr:class='data:post.oldLinkClass' expr:href='data:post.oldestLinkUrl'>
            <data:post.oldestLinkText/>
          </a>
          <a expr:class='data:post.oldLinkClass' expr:href='data:post.olderLinkUrl'>
            <data:post.olderLinkText/>
          </a>
          &#160;
          <data:post.commentRangeText/>
          &#160;
          <a expr:class='data:post.newLinkClass' expr:href='data:post.newerLinkUrl'>
            <data:post.newerLinkText/>
          </a>
          <a expr:class='data:post.newLinkClass' expr:href='data:post.newestLinkUrl'>
            <data:post.newestLinkText/>
          </a>
        </span>
      </b:if>
      <p class='comment-footer'>
<b:if cond='data:post.embedCommentForm'>
<b:include data='post' name='comment-form'/>
<b:else/>
<b:if cond='data:post.allowComments'>
<a expr:href='data:post.addCommentUrl' expr:onclick='data:post.addCommentOnclick'><data:postCommentMsg/></a>
</b:if>
</b:if>
</p>
    </div><!--end commentblock-->
</div>
    </b:if>

Salve e vizualize se está tudo certinho!
Beijos e comentem!