silahkan cari kode ]]></b:skin> atau </style> dan pastekan kode berikut diatasnya
/* Kotak Komentar */jika sudah ada kode komentar seperti diatas , silahkan diganti.
#threaded-comment-form p{letter-spacing:0.8px;position:relative;border:1px solid #999;background-color:#E5E5E5;background:-webkit-gradient( linear,left top,left bottom,color-stop(.2,white),color-stop(1,#EDEDED) );background:-moz-linear-gradient( center top,white 20%,#EDEDED 100% );padding:16px;font-size:12px;line-height:1.4em;color:#000;margin:0 0 12px 5px;font-family:coda;border-radius:4px 4px 4px 4px}
#threaded-comment-form p::before{top:100%;border:solid transparent;content:"";height:0;width:0;position:absolute}
#threaded-comment-form p::before{border-top-color:#fff;border-width:12px;left:6%;margin-left:-28px}
.comments .comment-thread.inline-thread .comment .comment-block:target{border:1px dashed yellow}
.comments{background:#DDD;margin:0;padding:0;border-left:1px solid #ccc;border-right:1px solid #ccc;}
#comments h4{background:#f8f8f8;border-top:1px solid #CCC;border-bottom:1px solid #CCC;color:#000;display:block;font-size:14px;font-weight:bold;padding:10px;position:relative;text-align:center}
.comments .comment-header,.comments .comment-thread.inline-thread .comment{position:relative}
.comment-thread ol{margin:0 0 18px}
.comments-content{padding:10px}
.comments .comments-content .comment-thread ol{list-style-type:none}
.comments .comments-content .user{font-style:normal;font-weight:bold}
.comments .avatar-image-container{float:left;max-height:50px;overflow:hidden;width:50px;background:#f5f5f5;border-radius:100%;margin:5px;}
.comments .avatar-image-container img{max-width:45px;height:45px;padding:4px;border-radius:100%;}
.avatar-image-container{border:1px solid #ccc;float:left;max-height:45px;overflow:hidden;padding:5px;width:45px}
.comments .comments-content .comment-header,.comments .comments-content .comment-content{border-bottom:1px solid #999;box-shadow:0 1px 0 #fff;display:block;margin-bottom:-1px!important;padding:6px}
.comments .comments-content .comment-content,.spammer-detected{font:13px/140% 'Coda',Calibri,'Myriad Pro',Myriad,'Trebuchet MS',Helvetica,Arial,sans-serif;color:#000;margin-bottom:0;padding:10px;text-align:justify}
.comments .comment-block,.comments .comments-content .comment-replies,.comments .comment-replybox-single{margin-left:72px}
.comments .comment-block,.comments .comment-thread.inline-thread .comment{border:1px solid #999;background-color:#E5E5E5;background:-webkit-gradient( linear,left top,left bottom,color-stop(.2,white),color-stop(1,#EDEDED) );background:-moz-linear-gradient( center top,white 20%,#EDEDED 100% );padding:10px;position:relative;border-radius:4px 4px 4px 4px}
.comments .comments-content .datetime a:link,.comments .comments-content .datetime a:visited{float:right!important;font-family:cambria,georgia,serif;color:#888!important;font-size:10px;padding:2px 10px}
.comment-replies .comment-block{box-shadow:none}
.comments .comments-content .comment{margin:2px 0 0;padding:0;width:100%}
.comments .comments-content .inline-thread{padding:0;margin-bottom:-16px}
.comments .comments-content .comment-replies{position:relative}
.comments .comment-thread.inline-thread{border-left:5px solid #f5f5f5;background:transparent;margin:2% 10% 2% 15%;padding:10px;}
.comments .comment-thread.inline-thread .comment{width:auto;padding:0;background:transparent;border:none;box-shadow:none}
.comments .comment-thread.inline-thread .comment .comment-block{border:1px solid #999;background-color:#E5E5E5;background:-webkit-gradient( linear,left top,left bottom,color-stop(.2,white),color-stop(1,#EDEDED) );background:-moz-linear-gradient( center top,white 20%,#EDEDED 100% );border-radius:4px 4px 4px 4px;padding:10px}
.comments .continue{border-top:0;width:auto}
.comments .continue a{background:#fff;color:#000;font-family:coda;text-align:center;float:right;font-weight:normal;padding:0 6px}
.comments .continue a:before,.comments .comment .comment-actions a:before{color:#000;font:normal normal 100%/normal "FontAwesome";content:"\f055";margin-right:.2em}
#comment-editor{width:103%!important}
.comment-form{width:100%;max-width:100%}
.comments .comments-content .loadmore{cursor:pointer;margin-top:3em;max-height:3em}
.comments .comments-content .loadmore.loaded{max-height:0;opacity:0;overflow:hidden}
.comments .thread-chrome.thread-collapsed,.comment .continue{margin:0;bottom:0;padding:0.6px 0;position:absolute}
.comments .comment .comment-actions a{padding:0 0 1px;display:block;position:absolute;top:65px;left:-60px;width:52px;text-align:center;border:1px solid #ccc;background-color:#EDEDED;background:-webkit-gradient( linear,left top,left bottom,color-stop(.2,white),color-stop(1,#E5E5E5) );background:-moz-linear-gradient( center top,white 20%,#E5E5E5 100% );font:11px/18px sans-serif;color:#333;font-size:12px}
.comments .comment .comment-actions a:hover,.comments .continue a:hover{text-decoration:none!important;color:#0070b0;background-color:#eee}
.comment-thread .comment-content a,.comments .user a,.comments .comment-thread.inline-thread .user a{color:#346FC9!important}
.comments .thread-toggle{display:none}
.comments .comments-content .icon.blog-author{content:"";display:block;width:100%;height:4px;background-color:#4b8db5;background-image:-webkit-linear-gradient(left,#f3a01e,#D05D2A,#9dc425,#4b8db5,#7c48b5);background-image:-moz-linear-gradient(left,#f3a01e,#D05D2A,#9dc425,#4b8db5,#7c48b5);background-image:-ms-linear-gradient(left,#f3a01e,#D05D2A,#9dc425,#4b8db5,#7c48b5);background-image:-o-linear-gradient(left,#f3a01e,#D05D2A,#9dc425,#4b8db5,#7c48b5);background-image:linear-gradient(left,#f3a01e,#D05D2A,#9dc425,#4b8db5,#7c48b5);position:absolute;bottom:0;left:0}
.comment-footer{display:none;color:white;font-weight:bold;padding:0 0 10px;text-shadow:1px 1px #000000}
.comments .comment-block:before{border-color:transparent #f5f5f5 transparent transparent;border-style:solid;border-width:12px;bottom:0;content:"";display:block;height:0;left:-25px;position:absolute;top:14px;width:0}
.comments .comment-block:after{border-color:transparent #f5f5f5 transparent transparent;border-style:solid;border-width:13px;bottom:0;content:"";display:block;height:0;left:-25px;position:absolute;top:13.2px;width:0}
#comment-editor{background:transparent url('https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgzsu5Yf51baIMxX4zt6ht0_iz00k_fMwSzi8wtbXbn1c3BtL2hSlM1k7GtMTon4mQAUvgfea7qth94zDZV_sgJssGfQ-9Sru3Fn2_zNRi8Hawdt7mphwNi6JcYrAWvKgMjryYQTSck930j/s1600/ajax-loader+(2).gif') no-repeat 50% 30%}
.comments .comments-content .datetime:before{color:#888;content:"Berkomentar...";margin-left:.4em}
.comments .comment-thread.inline-thread .datetime:before{color:#888;content:"Membalas...";margin-left:.4em}
/* Efek thread-comment bertingkat hanya dengan CSS */
.comments .comment-thread.inline-thread .comment{margin:2px 0 0 -50px}
source : http://de5ain.blogspot.com/2013/07/css-thread-comments-timeline-ala-de5ain.html