My Preference:

  
  
    
      "tweet" or "article" or "blog post" or "forum post" content goes here...
      
        Comments
        
          
            
              comment goes here...  
            
          
              
            
              comment goes here
            
          
          ....... more comments
        
      
          
  

I think comments are part of an article as they are closely related to the specific article. so I left comments inside the article element but within the section element to group them. If I wrap each comment inside an article element then it means each comment is distributable independently and still self-contained, which is not possible as each comment is related to the topic of an article. so I decided to wrap each comment within div. So, given HTML structure aligns best according to semantic meaning.