diff --git a/wp-includes/author-template.php b/wp-includes/author-template.php
index 2a89498968..557a1ab8c9 100644
--- a/wp-includes/author-template.php
+++ b/wp-includes/author-template.php
@@ -26,6 +26,13 @@ function get_the_author($deprecated = '') {
 	if ( !empty( $deprecated ) )
 		_deprecated_argument( __FUNCTION__, '2.1' );
 
+	/**
+	 * Filter the display name of the current post's author.
+	 *
+	 * @since 2.9.0
+	 *
+	 * @param string $authordata->display_name The author's display name.
+	 */
 	return apply_filters('the_author', is_object($authordata) ? $authordata->display_name : null);
 }
 
@@ -71,6 +78,14 @@ function the_author( $deprecated = '', $deprecated_echo = true ) {
 function get_the_modified_author() {
 	if ( $last_id = get_post_meta( get_post()->ID, '_edit_last', true) ) {
 		$last_user = get_userdata($last_id);
+
+		/**
+		 * Filter the display name of the author who last edited the current post.
+		 *
+		 * @since 2.8.0
+		 *
+		 * @param string $last_user->display_name The author's display name.
+		 */
 		return apply_filters('the_modified_author', $last_user->display_name);
 	}
 }
@@ -108,6 +123,16 @@ function get_the_author_meta( $field = '', $user_id = false ) {
 
 	$value = isset( $authordata->$field ) ? $authordata->$field : '';
 
+	/**
+	 * Filter the value of the requested user metadata.
+	 *
+	 * The filter name is dynamic and depends on the $field parameter of the function.
+	 *
+	 * @since 2.8.0
+	 *
+	 * @param string $value   The value of the metadata.
+	 * @param int    $user_id The user ID.
+	 */
 	return apply_filters( 'get_the_author_' . $field, $value, $user_id );
 }
 
@@ -119,8 +144,20 @@ function get_the_author_meta( $field = '', $user_id = false ) {
  * @param int $user_id Optional. User ID.
  * @echo string The author's field from the current author's DB object.
  */
-function the_author_meta($field = '', $user_id = false) {
-	echo apply_filters('the_author_' . $field, get_the_author_meta($field, $user_id), $user_id);
+function the_author_meta( $field = '', $user_id = false ) {
+	$author_meta = get_the_author_meta( $field, $user_id );
+
+	/**
+	 * The value of the requested user metadata.
+	 *
+	 * The filter name is dynamic and depends on the $field parameter of the function.
+	 *
+	 * @since 2.8.0
+	 *
+	 * @param string $author_meta The value of the metadata.
+	 * @param int    $user_id     The user ID.
+	 */
+	echo apply_filters( 'the_author_' . $field, $author_meta, $user_id );
 }
 
 /**
@@ -204,6 +241,14 @@ function the_author_posts_link($deprecated = '') {
 		esc_attr( sprintf( __( 'Posts by %s' ), get_the_author() ) ),
 		get_the_author()
 	);
+
+	/**
+	 * Filter the link to the author page of the author of the current post.
+	 *
+	 * @since 2.9.0
+	 *
+	 * @param string $link HTML link.
+	 */
 	echo apply_filters( 'the_author_posts_link', $link );
 }
 
@@ -232,7 +277,16 @@ function get_author_posts_url($author_id, $author_nicename = '') {
 		$link = home_url( user_trailingslashit( $link ) );
 	}
 
-	$link = apply_filters('author_link', $link, $author_id, $author_nicename);
+	/**
+	 * Filter the URL to the author's page.
+	 *
+	 * @since 2.1.0
+	 *
+	 * @param string $link            The URL to the author's page.
+	 * @param int    $author_id       The author's id.
+	 * @param string $author_nicename The author's nice name.
+	 */
+	$link = apply_filters( 'author_link', $link, $author_id, $author_nicename );
 
 	return $link;
 }
@@ -378,6 +432,13 @@ function is_multi_author() {
 		set_transient( 'is_multi_author', $is_multi_author );
 	}
 
+	/**
+	 * Filter whether the site has more than one author with published posts.
+	 *
+	 * @since 3.2.0
+	 *
+	 * @param bool $is_multi_author Whether $is_multi_author should evaluate as true.
+	 */
 	return apply_filters( 'is_multi_author', (bool) $is_multi_author );
 }