Update note from review comments

Author: afs

spec/index.html

@@ -613,7 +613,7 @@ <h3>IRIs</h3>
         An IRI reference is common usage of an Internationalized Resource Identifier.
         An IRI reference refers to either a resolved <a>IRI</a> or <a>relative IRI reference</a>,
         as described by the <em>IRI-reference</em> production in <a href="#iri-abnf" class="sectionRef"></a>.
-        The abstract syntax uses only fully resolved <a>IRIs</a>.
+        The abstract syntax uses only fully resolved <a>IRIs</a>.</p>
         When IRIs are used in operations that are only
         defined for URIs, they must first be converted according to
         the mapping defined in
@@ -642,9 +642,13 @@ <h3>IRIs</h3>
         if a <a data-cite="rfc3986#section-5.1">base IRI
         can be established</a> [[RFC3986]].</p>
 
-      <p><strong>URI Schemes:</strong> Examples of scheme-specific rules include the
-        <a data-cite="RFC7230#section-2.7.1">scheme rules for HTTP</a> and the
+      <p><strong>URI Schemes:</strong>
+        Implementations are encouraged to enforce the scheme-specific rules of
+        the common schemes, such as the
+        <a data-cite="RFC7230#section-2.7.1">scheme rules for HTTP/HTTPS</a> and the
         <a data-cite="did-core#identifier">DID syntax</a>.
+        Implementations ignore URI scheme rules
+        for schemes they do not recognize. 
       </p>
 
       <p><strong>IRI normalization:</strong>