diff --git a/modules/dt.init.less b/modules/dt.init.less
index e1122119a..8407279f4 100644
--- a/modules/dt.init.less
+++ b/modules/dt.init.less
@@ -113,17 +113,11 @@ h1, h2, h3, h4, h5, h6 {
 	position: absolute;
 	pointer-events: none;
 	opacity: 0;
-}
-
-/* stylelint-disable-next-line plugin/no-unsupported-browser-features */
-@supports ( mix-blend-mode: darken ) {
-	.ext-discussiontools-init-highlight {
-		/* stylelint-disable-next-line plugin/no-unsupported-browser-features */
-		mix-blend-mode: darken;
-		// Support: Safari
-		// Safari doesn't blend this overlay with the text unless GPU rendering is forced.
-		transform: translateZ( 0 );
-	}
+	/* stylelint-disable-next-line plugin/no-unsupported-browser-features */
+	mix-blend-mode: darken;
+	// Support: Safari
+	// Safari doesn't blend this overlay with the text unless GPU rendering is forced.
+	transform: translateZ( 0 );
 }
 
 .ext-discussiontools-init-highlight-fadein {
@@ -136,31 +130,13 @@ h1, h2, h3, h4, h5, h6 {
 }
 
 .ext-discussiontools-init-publishedcomment {
-	// Support: IE11
-	// On supporting browsers, we instead use non-transparent color with mix-blend-mode.
-	// Identical to #ffe29e on white background.
-	background-color: rgba( 255, 198, 60, 0.5 );
-}
-
-/* stylelint-disable-next-line plugin/no-unsupported-browser-features */
-@supports ( mix-blend-mode: darken ) {
-	.ext-discussiontools-init-publishedcomment {
-		background-color: #ffe29e;
-	}
+	background-color: #ffe29e;
 }
 
 .ext-discussiontools-init-targetcomment {
-	// Support: IE11, see above
-	background-color: rgba( 216, 235, 255, 0.5 );
-}
-
-/* stylelint-disable-next-line plugin/no-unsupported-browser-features */
-@supports ( mix-blend-mode: darken ) {
-	.ext-discussiontools-init-targetcomment {
-		// Same color as the :target selector for references (from Cite).
-		// Not sure if that's a good idea, but it should be different from -publishedcomment.
-		background-color: #eaf3ff;
-	}
+	// Same color as the :target selector for references (from Cite).
+	// Not sure if that's a good idea, but it should be different from -publishedcomment.
+	background-color: #eaf3ff;
 }
 
 // Topic subscriptions (both kinds)
diff --git a/modules/utils.js b/modules/utils.js
index 4c3ab93dc..b9eba2ee2 100644
--- a/modules/utils.js
+++ b/modules/utils.js
@@ -164,22 +164,6 @@ function childIndexOf( child ) {
 	return i;
 }
 
-/**
- * Check whether a Node contains (is an ancestor of) another Node (or is the same node)
- *
- * @param {Node} ancestor
- * @param {Node} descendant
- * @return {boolean}
- */
-function contains( ancestor, descendant ) {
-	// Support: IE 11
-	// Node#contains is only supported on HTMLElement nodes. Otherwise we could just use
-	// `ancestor.contains( descendant )`.
-	return ancestor === descendant ||
-		// eslint-disable-next-line no-bitwise
-		ancestor.compareDocumentPosition( descendant ) & Node.DOCUMENT_POSITION_CONTAINED_BY;
-}
-
 /**
  * Find closest ancestor element using one of the given tag names.
  *
@@ -327,7 +311,7 @@ function getCoveredSiblings( range ) {
 	if ( ancestor === range.startContainer ) {
 		start = range.startOffset;
 	} else {
-		while ( !contains( siblings[ start ], range.startContainer ) ) {
+		while ( !siblings[ start ].contains( range.startContainer ) ) {
 			start++;
 		}
 	}
@@ -336,7 +320,7 @@ function getCoveredSiblings( range ) {
 	if ( ancestor === range.endContainer ) {
 		end = range.endOffset - 1;
 	} else {
-		while ( !contains( siblings[ end ], range.endContainer ) ) {
+		while ( !siblings[ end ].contains( range.endContainer ) ) {
 			end--;
 		}
 	}