diff --git a/wp-includes/comment.php b/wp-includes/comment.php
index 77bc6171ee..bf4f430e41 100644
--- a/wp-includes/comment.php
+++ b/wp-includes/comment.php
@@ -2208,9 +2208,16 @@ function wp_throttle_comment_flood( $block, $time_lastcomment, $time_newcomment
 function wp_new_comment( $commentdata, $wp_error = false ) {
 	global $wpdb;
 
+	/*
+	 * Normalize `user_ID` to `user_id`, but pass the old key
+	 * to the `preprocess_comment` filter for backward compatibility.
+	 */
 	if ( isset( $commentdata['user_ID'] ) ) {
 		$commentdata['user_ID'] = (int) $commentdata['user_ID'];
 		$commentdata['user_id'] = $commentdata['user_ID'];
+	} elseif ( isset( $commentdata['user_id'] ) ) {
+		$commentdata['user_id'] = (int) $commentdata['user_id'];
+		$commentdata['user_ID'] = $commentdata['user_id'];
 	}
 
 	$prefiltered_user_id = ( isset( $commentdata['user_id'] ) ) ? (int) $commentdata['user_id'] : 0;
@@ -2235,11 +2242,13 @@ function wp_new_comment( $commentdata, $wp_error = false ) {
 
 	$commentdata['comment_post_ID'] = (int) $commentdata['comment_post_ID'];
 
+	// Normalize `user_ID` to `user_id` again, after the filter.
 	if ( isset( $commentdata['user_ID'] ) && $prefiltered_user_id !== (int) $commentdata['user_ID'] ) {
 		$commentdata['user_ID'] = (int) $commentdata['user_ID'];
 		$commentdata['user_id'] = $commentdata['user_ID'];
 	} elseif ( isset( $commentdata['user_id'] ) ) {
 		$commentdata['user_id'] = (int) $commentdata['user_id'];
+		$commentdata['user_ID'] = $commentdata['user_id'];
 	}
 
 	$commentdata['comment_parent'] = isset( $commentdata['comment_parent'] ) ? absint( $commentdata['comment_parent'] ) : 0;
@@ -3587,7 +3596,6 @@ function wp_handle_comment_submission( $comment_data ) {
 
 	$commentdata = array(
 		'comment_post_ID' => $comment_post_id,
-		'user_ID'         => $user_id,
 	);
 
 	$commentdata += compact(
@@ -3596,7 +3604,8 @@ function wp_handle_comment_submission( $comment_data ) {
 		'comment_author_url',
 		'comment_content',
 		'comment_type',
-		'comment_parent'
+		'comment_parent',
+		'user_id'
 	);
 
 	/**
diff --git a/wp-includes/version.php b/wp-includes/version.php
index 7d4578969c..26e46c5719 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -16,7 +16,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '6.1-beta3-54488';
+$wp_version = '6.1-beta3-54489';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.