diff --git a/modules/dt.debug.js b/modules/dt.debug.js
index 3cca76b53..bac4d97b5 100644
--- a/modules/dt.debug.js
+++ b/modules/dt.debug.js
@@ -1,30 +1,86 @@
 var
 	Parser = require( 'ext.discussionTools.init' ).Parser,
+	modifier = require( 'ext.discussionTools.init' ).modifier,
+	utils = require( 'ext.discussionTools.init' ).utils,
 	highlighter = require( './highlighter.js' ),
 	parser = new Parser( document.getElementById( 'mw-content-text' ) ),
 	comments = parser.getCommentItems(),
 	threads = parser.getThreads(),
-	timestampRegexps = parser.getLocalTimestampRegexps();
+	timestampRegexps = parser.getLocalTimestampRegexps(),
+	debug = +( new mw.Uri().query.dtdebug ),
+	DEBUG_HIGHLIGHT = 1,
+	DEBUG_VOTE = 2,
+	DEBUG_VOTE_PERMISSIVE = 4;
 
-highlighter.markThreads( threads );
+// eslint-disable-next-line no-bitwise
+if ( debug & DEBUG_HIGHLIGHT ) {
+	highlighter.markThreads( threads );
 
-comments.forEach( function ( comment ) {
-	comment.signatureRanges.forEach( function ( signatureRange ) {
-		var signature, emptySignature, node, match;
+	// TODO: Use comment.signatureRanges to mark up signatures/timestamps
+	comments.forEach( function ( comment ) {
+		comment.signatureRanges.forEach( function ( signatureRange ) {
+			var signature, emptySignature, node, match;
 
-		node = signatureRange.endContainer;
-		match = parser.findTimestamp( node, timestampRegexps );
-		if ( !match ) {
-			return;
-		}
-		signature = parser.findSignature( node )[ 0 ];
-		emptySignature = signature.length === 1 && signature[ 0 ] === node;
-		// Note that additional content may follow the timestamp (e.g. in some voting formats), but we
-		// don't care about it. The code below doesn't mark that due to now the text nodes are sliced,
-		// but we might need to take care to use the matched range of node in other cases.
-		highlighter.markTimestamp( parser, node, match );
-		if ( !emptySignature ) {
-			highlighter.markSignature( signature );
+			node = signatureRange.endContainer;
+			match = parser.findTimestamp( node, timestampRegexps );
+			if ( !match ) {
+				return;
+			}
+			signature = parser.findSignature( node )[ 0 ];
+			emptySignature = signature.length === 1 && signature[ 0 ] === node;
+			// Note that additional content may follow the timestamp (e.g. in some voting formats), but we
+			// don't care about it. The code below doesn't mark that due to now the text nodes are sliced,
+			// but we might need to take care to use the matched range of node in other cases.
+			highlighter.markTimestamp( parser, node, match );
+			if ( !emptySignature ) {
+				highlighter.markSignature( signature );
+			}
+		} );
+	} );
+}
+
+// eslint-disable-next-line no-bitwise
+if ( ( debug & DEBUG_VOTE ) || ( debug & DEBUG_VOTE_PERMISSIVE ) ) {
+	threads.forEach( function ( thread ) {
+		var level, lastReply, listItem, firstVote,
+			firstComment = thread.replies[ 0 ];
+
+		if ( firstComment && firstComment.type === 'comment' ) {
+			// eslint-disable-next-line no-bitwise
+			if ( !( debug & DEBUG_VOTE_PERMISSIVE ) && firstComment.level <= 1 ) {
+				// Not in permissive vote mode, and first reply was not indented
+				return;
+			}
+
+			firstVote = firstComment.level === 1 ?
+				// In permissive mode, the first vote is the replies to the OP
+				firstComment.replies[ 0 ] :
+				firstComment;
+
+			if ( !firstVote ) {
+				return;
+			}
+
+			level = firstVote.level;
+			firstVote.parent.replies.forEach( function ( reply ) {
+				if ( reply.type === 'comment' && reply.level <= level ) {
+					lastReply = reply;
+				}
+			} );
+
+			listItem = modifier.addSiblingListItem(
+				utils.closestElement( lastReply.range.endContainer, [ 'li', 'dd', 'p' ] )
+			);
+			if ( listItem && listItem.tagName.toLowerCase() === 'li' ) {
+				$( listItem )
+					// Hide bullet/number
+					.css( 'list-style', 'none' )
+					.append(
+						'[ ',
+						$( '<a>' ).text( 'add comment' ),
+						' ]'
+					);
+			}
 		}
 	} );
-} );
+}