diff --git a/includes/CommentModifier.php b/includes/CommentModifier.php
index e07c17b0c..edc6827e9 100644
--- a/includes/CommentModifier.php
+++ b/includes/CommentModifier.php
@@ -368,10 +368,6 @@ class CommentModifier {
 	 * @param DocumentFragment|null $fragment Containing document fragment if list has no parent
 	 */
 	public static function unwrapList( Node $list, ?DocumentFragment $fragment = null ): void {
-		$doc = $list->ownerDocument;
-		$container = $fragment ?: $list->parentNode;
-		$referenceNode = $list;
-
 		if ( !(
 			$list instanceof Element && (
 				strtolower( $list->tagName ) === 'dl' ||
@@ -388,6 +384,9 @@ class CommentModifier {
 			return;
 		}
 
+		$doc = $list->ownerDocument;
+		$container = $fragment ?: $list->parentNode;
+		$referenceNode = $list;
 		while ( $list->firstChild ) {
 			if ( $list->firstChild instanceof Element ) {
 				// Move <dd> contents to <p>
diff --git a/modules/.eslintrc.json b/modules/.eslintrc.json
index 7c9627ad0..2a6c69aec 100644
--- a/modules/.eslintrc.json
+++ b/modules/.eslintrc.json
@@ -11,7 +11,6 @@
 	},
 	"rules": {
 		"no-implicit-globals": "off",
-		"prefer-const": "off",
 		"max-len": "off",
 		"prefer-arrow-callback": "error",
 		"implicit-arrow-linebreak": "error",
diff --git a/modules/CommentController.js b/modules/CommentController.js
index 6babc2cb1..10f225ee0 100644
--- a/modules/CommentController.js
+++ b/modules/CommentController.js
@@ -671,10 +671,10 @@ CommentController.prototype.getUnsupportedNodeSelectors = function () {
  * @return {jQuery.Promise} Promise which resolves when switch is complete
  */
 CommentController.prototype.switchToVisual = function () {
-	let oldWidget = this.replyWidget,
+	const oldWidget = this.replyWidget,
 		oldShowAdvanced = oldWidget.showAdvanced,
-		oldEditSummary = oldWidget.getEditSummary(),
-		wikitext = oldWidget.getValue();
+		oldEditSummary = oldWidget.getEditSummary();
+	let wikitext = oldWidget.getValue();
 
 	// Replace wikitext signatures with a special marker recognized by DtDmMWSignatureNode
 	// to render them as signature nodes in visual mode.
diff --git a/modules/Parser.js b/modules/Parser.js
index f044aaee0..7f12ddde1 100644
--- a/modules/Parser.js
+++ b/modules/Parser.js
@@ -516,11 +516,10 @@ function acceptOnlyNodesAllowingComments( node ) {
  *   - {Object} range Range-like object covering the timestamp
  */
 Parser.prototype.findTimestamp = function ( node, timestampRegexps ) {
-	let matchData, i,
-		nodeText = '',
-		offset = 0,
-		// Searched nodes (reverse order)
-		nodes = [];
+	let nodeText = '';
+	let offset = 0;
+	// Searched nodes (reverse order)
+	const nodes = [];
 
 	while ( node ) {
 		nodeText = node.nodeValue + nodeText;
@@ -554,12 +553,12 @@ Parser.prototype.findTimestamp = function ( node, timestampRegexps ) {
 		}
 	}
 
-	for ( i = 0; i < timestampRegexps.length; i++ ) {
+	for ( let i = 0; i < timestampRegexps.length; i++ ) {
 		// Technically, there could be multiple matches in a single text node. However, the ultimate
 		// point of this is to find the signatures which precede the timestamps, and any later
 		// timestamps in the text node can't be directly preceded by a signature (as we require them to
 		// have links), so we only concern ourselves with the first match.
-		matchData = nodeText.match( timestampRegexps[ i ] );
+		const matchData = nodeText.match( timestampRegexps[ i ] );
 		if ( matchData ) {
 			const timestampLength = matchData[ 0 ].length;
 			// Bytes at the end of the last node which aren't part of the match
diff --git a/modules/controller.js b/modules/controller.js
index 49d3e72f9..896727d8e 100644
--- a/modules/controller.js
+++ b/modules/controller.js
@@ -251,9 +251,9 @@ function getCheckboxesPromise( pageName, oldId ) {
  * @return {string[]}
  */
 function getReplyWidgetModules() {
-	let veConf = mw.config.get( 'wgVisualEditorConfig' ),
-		modules = [ 'ext.discussionTools.ReplyWidget' ]
-			.concat( veConf.pluginModules.filter( mw.loader.getState ) );
+	const veConf = mw.config.get( 'wgVisualEditorConfig' );
+	let modules = [ 'ext.discussionTools.ReplyWidget' ]
+		.concat( veConf.pluginModules.filter( mw.loader.getState ) );
 
 	if ( OO.ui.isMobile() ) {
 		modules = [
@@ -281,9 +281,9 @@ function getReplyWidgetModules() {
 function init( $container, state ) {
 	let
 		activeCommentId = null,
-		activeController = null,
-		// Loads later to avoid circular dependency
-		CommentController = require( './CommentController.js' ),
+		activeController = null;
+	// Loads later to avoid circular dependency
+	const CommentController = require( './CommentController.js' ),
 		NewTopicController = require( './NewTopicController.js' );
 
 	// We may be re-initializing after posting a new comment, so clear the cache, because
diff --git a/modules/dt-ve/dt.ui.UsernameCompletionAction.js b/modules/dt-ve/dt.ui.UsernameCompletionAction.js
index 952b94e61..a3ceea0f2 100644
--- a/modules/dt-ve/dt.ui.UsernameCompletionAction.js
+++ b/modules/dt-ve/dt.ui.UsernameCompletionAction.js
@@ -1,5 +1,5 @@
 const controller = require( 'ext.discussionTools.init' ).controller;
-let sequence;
+let sequence = null;
 
 function sortAuthors( a, b ) {
 	return a.username < b.username ? -1 : ( a.username === b.username ? 0 : 1 );
@@ -67,8 +67,8 @@ MWUsernameCompletionAction.static.methods.push( 'insertAndOpen' );
 /* Methods */
 
 MWUsernameCompletionAction.prototype.insertAndOpen = function () {
-	let inserted = false,
-		surfaceModel = this.surface.getModel(),
+	let inserted = false;
+	const surfaceModel = this.surface.getModel(),
 		fragment = surfaceModel.getFragment();
 
 	// This is opening a window in a slightly weird way, so the normal logging
diff --git a/modules/modifier.js b/modules/modifier.js
index 9c8fc441e..3996059c0 100644
--- a/modules/modifier.js
+++ b/modules/modifier.js
@@ -310,10 +310,6 @@ function removeAddedListItem( node ) {
  * @param {DocumentFragment|null} fragment Containing document fragment if list has no parent
  */
 function unwrapList( list, fragment ) {
-	let doc = list.ownerDocument,
-		container = fragment || list.parentNode,
-		referenceNode = list;
-
 	if ( !(
 		list.nodeType === Node.ELEMENT_NODE && (
 			list.tagName.toLowerCase() === 'dl' ||
@@ -330,7 +326,9 @@ function unwrapList( list, fragment ) {
 		return;
 	}
 
-	let insertBefore;
+	const doc = list.ownerDocument;
+	const container = fragment || list.parentNode;
+	let referenceNode = list;
 	while ( list.firstChild ) {
 		if ( list.firstChild.nodeType === Node.ELEMENT_NODE ) {
 			// Move <dd> contents to <p>
@@ -340,11 +338,11 @@ function unwrapList( list, fragment ) {
 				// and start a new paragraph after
 				if ( utils.isBlockElement( list.firstChild.firstChild ) ) {
 					if ( p.firstChild ) {
-						insertBefore = referenceNode.nextSibling;
+						const insertBefore2 = referenceNode.nextSibling;
 						referenceNode = p;
-						container.insertBefore( p, insertBefore );
+						container.insertBefore( p, insertBefore2 );
 					}
-					insertBefore = referenceNode.nextSibling;
+					const insertBefore = referenceNode.nextSibling;
 					referenceNode = list.firstChild.firstChild;
 					container.insertBefore( list.firstChild.firstChild, insertBefore );
 					p = doc.createElement( 'p' );
@@ -353,14 +351,14 @@ function unwrapList( list, fragment ) {
 				}
 			}
 			if ( p.firstChild ) {
-				insertBefore = referenceNode.nextSibling;
+				const insertBefore = referenceNode.nextSibling;
 				referenceNode = p;
 				container.insertBefore( p, insertBefore );
 			}
 			list.removeChild( list.firstChild );
 		} else {
 			// Text node / comment node, probably empty
-			insertBefore = referenceNode.nextSibling;
+			const insertBefore = referenceNode.nextSibling;
 			referenceNode = list.firstChild;
 			container.insertBefore( list.firstChild, insertBefore );
 		}
diff --git a/modules/topicsubscriptions.js b/modules/topicsubscriptions.js
index 334b51e55..1e4310344 100644
--- a/modules/topicsubscriptions.js
+++ b/modules/topicsubscriptions.js
@@ -321,7 +321,7 @@ function maybeShowFirstTimeAutoTopicSubPopup() {
 	mw.user.options.set( 'discussiontools-seenautotopicsubpopup', '1' );
 	api.saveOption( 'discussiontools-seenautotopicsubpopup', '1' );
 
-	let $popupContent, popup;
+	let popup = null;
 
 	function close() {
 		popup.$element.removeClass( 'ext-discussiontools-autotopicsubpopup-fadein' );
@@ -330,7 +330,7 @@ function maybeShowFirstTimeAutoTopicSubPopup() {
 		}, 1000 );
 	}
 
-	$popupContent = $( '<div>' )
+	const $popupContent = $( '<div>' )
 		.append(
 			$( '<strong>' )
 				.addClass( 'ext-discussiontools-autotopicsubpopup-title' )