Displaying star rating with Discourse is easy. I am happy to share, It can be done in simple few steps
Process 
Setup Google Tag Manager for your Discourse Application
 
Add a new HTML Tag containing JSON-LD markup
 
Filter trigger by page view  for particular URL
 
Publish, wait for 24 hrs to see the result in SERPs.
 
 
Thanks
             
            
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              Interesting. Where are you getting the rating from, Google?
             
            
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                neil  
              
                  
                    April 1, 2018,  3:40pm
                   
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Looks interesting and useful for other types of integrations with tag manager. Can you show what to add in head section of Discourse?
             
            
              
            
           
          
            
            
              Just by editing Theme, I added Tag Manager Script in the </head> section.
             
            
              
            
           
          
            
              
                neil  
              
                  
                    April 1, 2018,  4:18pm
                   
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              Oh but Discourse has a setting to do that for you. Search settings for GTM.
             
            
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              Good to know, we can add GTM script via Settings. Thanks for the hint about better way.
             
            
              
            
           
          
            
            
              @neil  There is one problem when I add GTM script via Discourse settings, it places inside body.
Expected : It should be in the head.
Previously, it was recommended by Google  to place in the body.
But now , they have updated their guidelines: “Paste this code as high in the  <head>   of the page as possible”.
Can we make this possible?
             
            
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                neil  
              
                  
                    April 1, 2018, 11:49pm
                   
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              Thanks for pointing that out. Yes we should change it to be in the head. Added to my list.
             
            
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                riking  
              
                  
                    April 2, 2018,  5:21am
                   
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              “As high in the <head> as possible”
… 
             
            
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                angus  
                
                  
                    April 2, 2018,  5:57am
                   
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              Depending on the kind of rating you’re after you can also use the ratings plugin , which automatically adds the average rating for a topic as structured data to the topic page html.
Example from a user here: Topic Ratings Plugin 
             
            
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                neil  
              
                  
                    April 3, 2018,  7:26pm
                   
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              @Gulshan_Kumar   I updated our GTM support today so it adds the code to the head and the body according to the new instructions.
             
            
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                PoojaPatel  
              
                  
                    April 14, 2019,  2:19pm
                   
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              Currently I could not see star rating showing in SERP for above two post.
Bunny CDN Review. 
Obstetrics and Cynecology at studmed.dk 
 
@Gulshan_Kumar   - are you removing star rating in gtm or use any method?
             
            
              
            
           
          
            
            
              The method which I suggested (using GTM+JSON-LD for star rating) works completely fine. You can continue to use it.
In my case, I intentionally removed from that post due to some personal reason. Nothing else.
             
            
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