Index: src/wp-content/themes/twentyfifteen/inc/customizer.php
===================================================================
--- src/wp-content/themes/twentyfifteen/inc/customizer.php	(revision 30089)
+++ src/wp-content/themes/twentyfifteen/inc/customizer.php	(working copy)
@@ -415,8 +415,8 @@
 		.comment-content a:focus,
 		.author-description a:hover,
 		.author-description a:focus {
-			border-color: %4$s; /* Fallback for IE7 and IE8 */
-			border-color: %5$s;
+			color: %4$s; /* Fallback for IE7 and IE8 */
+			color: %5$s;
 		}
 
 		/* Border Color */
Index: src/wp-content/themes/twentyfifteen/style.css
===================================================================
--- src/wp-content/themes/twentyfifteen/style.css	(revision 30089)
+++ src/wp-content/themes/twentyfifteen/style.css	(working copy)
@@ -1174,7 +1174,55 @@
 	z-index: 100000;
 }
 
+a:focus,
+a:hover {
+	text-decoration: underline;
+}
 
+.entry-content a:focus,
+.entry-content a:hover,
+.social-navigation a:focus:before,
+.social-navigation a:hover:before,
+.comment-reply-title small a:focus:before,
+.comment-reply-title small a:hover:before,
+.comment-navigation .nav-next a:focus:after,
+.comment-navigation .nav-next a:hover:after,
+.comment-navigation .nav-previous a:focus:before,
+.comment-navigation .nav-previous a:hover:before,
+.posted-on a:focus:before,
+.posted-on a:hover:before,
+.byline a:focus:before,
+.byline a:hover:before,
+.cat-links span + a:focus:before,
+.cat-links span + a:hover:before,
+.tags-links span + a:focus:before,
+.tags-links span + a:hover:before,
+.comments-link a:focus:before,
+.comments-link a:hover:before,
+.entry-format a:focus:before,
+.entry-format a:hover:before,
+.edit-link a:focus:before,
+.edit-link a:hover:before,
+.full-size-link a:focus:before,
+.full-size-link a:hover:before,
+.pagination .prev:focus:before,
+.pagination .prev:focus:before,
+.pagination .next:focus:before,
+.pagination .next:hover:before,
+.image-navigation a:focus:before,
+.image-navigation a:hover:before,
+.image-navigation a:focus:after,
+.image-navigation a:hover:after,
+.format-link .entry-title a:focus:after,
+.format-link .entry-title a:hover:after,
+.entry-content .more-link:focus:after,
+.entry-content .more-link:hover:after,
+.author-link:focus:after,
+.author-link:hover:after {
+	text-decoration: none;
+	border-bottom: none;
+}
+
 /**
  * 8.0 Alignments
  */
@@ -1712,8 +1760,7 @@
 .page-content a:focus,
 .comment-content a:hover,
 .comment-content a:focus {
-	border-color: #707070;
-	border-color: rgba(51, 51, 51, 0.7);
+	border: none;
 	color: #707070;
 	color: rgba(51, 51, 51, 0.7);
 }