Hi there, as what @Canapin  said above, Discourse doesn’t use nested replies.
Not quite the same, but when posts have replies to, you can see an arrow with a button with the number of replies, where clicking it will show replies (kind of threaded-like):
You can can something similar with this plugin too:
  
  
    How to install plugins in Discourse 
Watch this video for an introduction to the plugin: 
 
 
 
And perhaps:
  
  
    [post voting toggle]  
With the topic in Post Voting mode, there’s a filter to sort answers by votes or by activity. Here’s an example …
   
 
             
            
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