Index: wp-content/themes/twentyfifteen/style.css
===================================================================
--- wp-content/themes/twentyfifteen/style.css	(revision 61637)
+++ wp-content/themes/twentyfifteen/style.css	(working copy)
@@ -6152,3 +6152,9 @@
 		padding: 0;
 	}
 }
+.wp-block-quote:where(.has-text-align-right) {
+    border-left: none;
+    border-right: .25em solid;
+    padding-left: 0;
+    padding-right: 1em
+}
\ No newline at end of file