Edit in JSFiddle

<template id="commentTemplate">
    <div>
        <img src="">
        <div class="comment-text"></div>
    </div>
</template>

function addComment(imageUrl, text) {
    var t = document.querySelector("#commentTemplate"),
        comment = t.content.cloneNode(true);

    comment.querySelector('img').src = imageUrl;
    comment.querySelector('.comment-text').textContent = text;
    document.body.appendChild(comment);
}

addComment("http://daker.me/assets/images/avatar.png", "This is a test comment");
addComment("http://daker.me/assets/images/avatar.png", "It working...");