diff --git a/wp-includes/comment.php b/wp-includes/comment.php
index 7da516266f..8a13723001 100644
--- a/wp-includes/comment.php
+++ b/wp-includes/comment.php
@@ -1121,6 +1121,37 @@ function wp_get_comment_fields_max_lengths() {
 	return apply_filters( 'wp_get_comment_fields_max_lengths', $lengths );
 }
 
+/**
+ * Compares the lengths of comment data against the maximum character limits.
+ *
+ * @since 4.7.0
+ *
+ * @param array $comment_data Array of arguments for inserting a comment.
+ * @return WP_Error|true WP_Error when a comment field exceeds the limit,
+ *                       otherwise true.
+ */
+function wp_check_comment_data_max_lengths( $comment_data ) {
+	$max_lengths = wp_get_comment_fields_max_lengths();
+
+	if ( isset( $comment_data['comment_author'] ) && mb_strlen( $comment_data['comment_author'], '8bit' ) > $max_lengths['comment_author'] ) {
+		return new WP_Error( 'comment_author_column_length', __( '<strong>ERROR</strong>: your name is too long.' ), 200 );
+	}
+
+	if ( isset( $comment_data['comment_author_email'] ) && strlen( $comment_data['comment_author_email'] ) > $max_lengths['comment_author_email'] ) {
+		return new WP_Error( 'comment_author_email_column_length', __( '<strong>ERROR</strong>: your email address is too long.' ), 200 );
+	}
+
+	if ( isset( $comment_data['comment_author_url'] ) && strlen( $comment_data['comment_author_url'] ) > $max_lengths['comment_author_url'] ) {
+		return new WP_Error( 'comment_author_url_column_length', __( '<strong>ERROR</strong>: your url is too long.' ), 200 );
+	}
+
+	if ( isset( $comment_data['comment_content'] ) && mb_strlen( $comment_data['comment_content'], '8bit' ) > $max_lengths['comment_content'] ) {
+		return new WP_Error( 'comment_content_column_length', __( '<strong>ERROR</strong>: your comment is too long.' ), 200 );
+	}
+
+	return true;
+}
+
 /**
  * Does comment contain blacklisted characters or words.
  *
@@ -3032,7 +3063,6 @@ function wp_handle_comment_submission( $comment_data ) {
 	}
 
 	$comment_type = '';
-	$max_lengths = wp_get_comment_fields_max_lengths();
 
 	if ( get_option( 'require_name_email' ) && ! $user->exists() ) {
 		if ( 6 > strlen( $comment_author_email ) || '' == $comment_author ) {
@@ -3042,22 +3072,8 @@ function wp_handle_comment_submission( $comment_data ) {
 		}
 	}
 
-	if ( isset( $comment_author ) && $max_lengths['comment_author'] < mb_strlen( $comment_author, '8bit' ) ) {
-		return new WP_Error( 'comment_author_column_length', __( '<strong>ERROR</strong>: your name is too long.' ), 200 );
-	}
-
-	if ( isset( $comment_author_email ) && $max_lengths['comment_author_email'] < strlen( $comment_author_email ) ) {
-		return new WP_Error( 'comment_author_email_column_length', __( '<strong>ERROR</strong>: your email address is too long.' ), 200 );
-	}
-
-	if ( isset( $comment_author_url ) && $max_lengths['comment_author_url'] < strlen( $comment_author_url ) ) {
-		return new WP_Error( 'comment_author_url_column_length', __( '<strong>ERROR</strong>: your url is too long.' ), 200 );
-	}
-
 	if ( '' == $comment_content ) {
 		return new WP_Error( 'require_valid_comment', __( '<strong>ERROR</strong>: please type a comment.' ), 200 );
-	} elseif ( $max_lengths['comment_content'] < mb_strlen( $comment_content, '8bit' ) ) {
-		return new WP_Error( 'comment_content_column_length', __( '<strong>ERROR</strong>: your comment is too long.' ), 200 );
 	}
 
 	$commentdata = compact(
@@ -3071,6 +3087,11 @@ function wp_handle_comment_submission( $comment_data ) {
 		'user_ID'
 	);
 
+	$check_max_lengths = wp_check_comment_data_max_lengths( $commentdata );
+	if ( is_wp_error( $check_max_lengths ) ) {
+		return $check_max_lengths;
+	}
+
 	$comment_id = wp_new_comment( wp_slash( $commentdata ), true );
 	if ( is_wp_error( $comment_id ) ) {
 		return $comment_id;
diff --git a/wp-includes/rest-api/endpoints/class-wp-rest-comments-controller.php b/wp-includes/rest-api/endpoints/class-wp-rest-comments-controller.php
index 3454dc1906..bfd652db4b 100644
--- a/wp-includes/rest-api/endpoints/class-wp-rest-comments-controller.php
+++ b/wp-includes/rest-api/endpoints/class-wp-rest-comments-controller.php
@@ -484,6 +484,12 @@ class WP_REST_Comments_Controller extends WP_REST_Controller {
 			$prepared_comment['comment_agent'] = '';
 		}
 
+		$check_comment_lengths = wp_check_comment_data_max_lengths( $prepared_comment );
+		if ( is_wp_error( $check_comment_lengths ) ) {
+			$error_code = $check_comment_lengths->get_error_code();
+			return new WP_Error( $error_code, __( 'Comment field exceeds maximum length allowed.' ), array( 'status' => 400 ) );
+		}
+
 		$prepared_comment['comment_approved'] = wp_allow_comment( $prepared_comment, true );
 
 		if ( is_wp_error( $prepared_comment['comment_approved'] ) ) {
@@ -631,6 +637,12 @@ class WP_REST_Comments_Controller extends WP_REST_Controller {
 
 			$prepared_args['comment_ID'] = $id;
 
+			$check_comment_lengths = wp_check_comment_data_max_lengths( $prepared_args );
+			if ( is_wp_error( $check_comment_lengths ) ) {
+				$error_code = $check_comment_lengths->get_error_code();
+				return new WP_Error( $error_code, __( 'Comment field exceeds maximum length allowed.' ), array( 'status' => 400 ) );
+			}
+
 			$updated = wp_update_comment( $prepared_args );
 
 			if ( 0 === $updated ) {
diff --git a/wp-includes/version.php b/wp-includes/version.php
index 5bae15fa8b..33599270ef 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '4.7-beta1-39100';
+$wp_version = '4.7-beta1-39101';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.