title: If the same val is used to replace two separate string.Format placeholders, must it be provided twice?
body: <p>Given this:</p>
  
  <pre><code>string msg = string.Format("Duckbill {0} Platypus has not been loaded. Fetch Duckbill {1}'s Platypus then continue.", userDuckbill, userDuckbill);
  </code></pre>
  
  <p>...would it suffice to do this instead:</p>
  
  <pre><code>string msg = string.Format("Duckbill {0} Platypus has not been loaded. Fetch Duckbill {1}'s Platypus then continue.", userDuckbill);
  </code></pre>
  
  <p>?</p>