title: Replacement steps in operation BlockDeclarationInstantiation
body: <p>Recently, I've noticed that operation <a href="https://tc39.es/ecma262/#sec-blockdeclarationinstantiation" rel="nofollow noreferrer">BlockDeclarationInstantiation</a> has some changes. Take a look at these points:</p>
  <blockquote>
  <p>Perform ! env.CreateMutableBinding(dn, false). NOTE: This step is
  replaced in section B.3.2.6.</p>
  </blockquote>
  <p>and</p>
  <blockquote>
  <p>Perform env.InitializeBinding(fn, fo). NOTE: This step is replaced in
  section B.3.2.6.</p>
  </blockquote>
  <p>Earlier I've not seen them.
  In draft specification we have for BlockDeclarationInstantiation <a href="https://tc39.es/ecma262/#sec-web-compat-blockdeclarationinstantiation" rel="nofollow noreferrer">this</a>.
  In comparison with <a href="https://262.ecma-international.org/7.0/#sec-additional-ecmascript-features-for-web-browsers" rel="nofollow noreferrer">ECMAScript 7</a> we have not this point, but in <a href="https://262.ecma-international.org/8.0/#sec-web-compat-blockdeclarationinstantiation" rel="nofollow noreferrer">ECMAScript 8</a> we have part of that what we have in the draft version.</p>
  <ol>
  <li>Why do we have so differences for BlockDeclarationInstantiation compability among versions? Shouldn't compatibility be the same?</li>
  <li>Why has not it done simple by inserting new points in current algorithm of BlockDeclarationInstantiation?</li>
  <li>What do replacements actual do especial that they didn't before?</li>
  </ol>