Editorial fixes based on #1015

index.html

@@ -614,7 +614,7 @@ <h2>
                     </ol>
                   </li>
                   <li>If |seenPMIs| [=set/contain|contains=] |pmi| throw a
-                  {{RangeError}} {{DOMException}} optionally letting the
+                  {{RangeError}} {{DOMException}} optionally informing the
                   developer this [=payment method identifier=] is a duplicate.
                   </li>
                   <li>[=set/Append=] |pmi| to |seenPMIs|.
@@ -2742,7 +2742,7 @@ <h2>
           |request|.{{PaymentRequest/[[response]]}} if |isRetry| is true, or a
           new {{PaymentResponse}} otherwise.
           </li>
-          <li>If |isRetry| if false, initialize the newly created |response|:
+          <li>If |isRetry| is false, initialize the newly created |response|:
             <ol>
               <li>Set |response|.{{PaymentResponse/[[request]]}} to |request|.
               </li>
@@ -3255,7 +3255,7 @@ <h2 id="canmakepayment-protections">
           The {{PaymentRequest/canMakePayment()}} method provides feature
           detection for different payment methods. It may become a
           fingerprinting vector if in the future, a large number of payment
-          methods are available. purposes. User agents are expected to protect
+          methods are available. User agents are expected to protect
           the user from abuse of the method. For example, user agents can
           reduce user fingerprinting by:
         </p>