After comment is added, button should go back to Close button.

app/assets/javascripts/notes.js.coffee

@@ -26,6 +26,7 @@ class Notes
     # Reopen and close actions for Issue/MR combined with note form submit
     $(document).on "click", ".js-note-target-reopen", @targetReopen
     $(document).on "click", ".js-note-target-close", @targetClose
+    $(document).on "click", ".js-comment-button", @updateCloseButton
     $(document).on "keyup", ".js-note-text", @updateTargetButtons
 
     # remove a note (in general)
@@ -496,6 +497,11 @@ class Notes
     if noteText.trim().length > 0
       form.submit()
 
+  updateCloseButton: (e) =>
+    textarea = $(e.target)
+    form = textarea.parents('form')
+    form.find('.js-note-target-close').text('Close')
+
   updateTargetButtons: (e) =>
     textarea = $(e.target)
     form = textarea.parents('form')