Write the HTML markup for several of (profile picture + message heading + message)
If it's all about semantic then let's see what HTML5 specs say (emphasis is mine):


  The article element represents a component of a page that consists of a self-contained composition in a document, page, application, or site and that is intended to be independently distributable or reusable, e.g. in syndication. This could be a forum post, a magazine or newspaper article, a blog entry, a user-submitted comment, an interactive widget or gadget, or any other independent item of content.


In this case it seems that &lt;article&gt; is an appropriate choice for your comments. Is it &lt;section&gt; an appropriate container? I don't think it is, specs says:


  The section element represents a generic document or application section…The section element is not a generic container element. When an element is needed only for styling purposes or as a convenience for scripting, authors are encouraged to use the div element instead. A general rule is that the section element is appropriate only if the element’s contents would be listed explicitly in the document’s outline.


I agree that interpretation can be little bit subjective here but I'd take it literally: you do not have a specific header for this section. In your case if &lt;section&gt; is not to group a section of your document (for example an outer &lt;article&gt; with its list of comments) then I'd use the good old &lt;div&gt;:

&lt;div class="comment-section"&gt;
  &lt;article&gt;
  &lt;/article&gt;
&lt;/div&gt;


If, however, comments are just a part (section) of your main document which you may want to see in document outline and not simply a styling container (remember that it's important for screen-readers and all the others assistive tools) then don't refrain and use &lt;section&gt;.



Now let's talk about article content. You're using &lt;h4&gt; for styling purposes. I don't see whole page outline then I can't comment on this but keep in mind that heading elements should be used to denote an hypothetical structure, not for their styling. Imagine to replace your &lt;h4&gt;Title&lt;/h4&gt; with &lt;div class="header"&gt;Title&lt;/div&gt; where div.header is appropriately styled. Does the meaning of your document is lost? If answer is no then you're using heading elements because of styling and you shouldn't.

HTML5 introduced a new element  which may be appropriate in your case:

&lt;div class="comment-section"&gt;
  &lt;article&gt;
      &lt;header&gt;...&lt;/header&gt;
  &lt;/article&gt;
&lt;/div&gt;


Note that even if you really want to keep  because of its meaning in document outline I'd wrap it inside an &lt;header&gt; section.

&lt;div class="comment-section"&gt;
  &lt;article&gt;
      &lt;header&gt;
          &lt;h4&gt;Title&lt;/h4&gt;
      &lt;/header&gt;
  &lt;/article&gt;
&lt;/div&gt;


What is it useful for? For example if tomorrow you will add subtitle to hold the date and the author of the comment...

Now let's think about &lt;img&gt;. First of all it has to have an alt attribute but I'd also consider to move it into its own &lt;aside&gt; element. It may help screen readers to keep "focus" on the content. About this...do not forget to include all the proper aria- attributes!