MAGETWO-51801: PR Creation & Stabilization

- To keep placeholder in place.

Author: Hayder Sharhan

app/code/Magento/Theme/i18n/en_US.csv

@@ -123,7 +123,7 @@ Hour,Hour
 Minute,Minute
 "We could not detect a size.","We could not detect a size."
 "We don't recognize this file extension.","We don't recognize this file extension."
-"Welcome, ","Welcome, "
+"Welcome, %1!","--Welcome, %1!"
 Empty,Empty
 "1 column","1 column"
 Configuration,Configuration

app/code/Magento/Theme/view/frontend/templates/html/header.phtml

@@ -15,8 +15,7 @@ $welcomeMessage = $block->getWelcome();
     case 'welcome': ?>
         <li class="greet welcome" data-bind="scope: 'customer'">
             <!-- ko if: customer().fullname  -->
-            <span><?php /* @noEscape */ echo __('Welcome, ');?></span>
-            <span><!-- ko text: customer().firstname + '!' --><!-- /ko --></span>
+            <span data-bind="text: new String('<?php echo __('Welcome, %1!', '%1');?>').replace('%1', customer().firstname)"></span>
             <!-- /ko -->
             <!-- ko ifnot: customer().fullname  -->
             <span data-bind="html:'<?=$block->escapeHtml($welcomeMessage) ?>'"></span>