Index: src/wp-includes/capabilities.php
===================================================================
--- src/wp-includes/capabilities.php	(revision 38213)
+++ src/wp-includes/capabilities.php	(working copy)
@@ -251,8 +251,16 @@
 
 		if ( $meta_key && ( has_filter( "auth_post_meta_{$meta_key}" ) || has_filter( "auth_post_{$post_type}_meta_{$meta_key}" ) ) ) {
 			/**
-			 * Filters whether the user is allowed to add post meta to a post.
+			 * auth_post_meta_{$meta_key} filters whether the user is allowed to edit post meta.
 			 *
+			 * If the filter is left at false, the capability to add, edit, or delete post meta will 
+			 * be added to the mapped edit_post capabilities. 
+			 *
+			 * If the filter is set to true, only the mapped meta caps from edit_post will apply. 
+			 *
+			 * Use the auth_post_{$post_type}_meta_{$meta_key} filter to modify capabilities for
+			 * specific post types. 
+			 *
 			 * The dynamic portion of the hook name, `$meta_key`, refers to the
 			 * meta key passed to map_meta_cap().
 			 *
@@ -268,8 +276,16 @@
 			$allowed = apply_filters( "auth_post_meta_{$meta_key}", false, $meta_key, $post->ID, $user_id, $cap, $caps );
 
 			/**
-			 * Filters whether the user is allowed to add post meta to a post of a given type.
+			 * auth_post_meta_{$meta_key} filters whether the user is allowed to edit post meta for
+			 * a post of a given type.
 			 *
+			 * If the filter is left at false, the capability to add, edit, or delete post meta will 
+			 * be added to the mapped edit_post capabilities. 
+			 *
+			 * If the filter is set to true, only the mapped meta caps from edit_post will apply. 
+			 *
+			 * Use the auth_post_meta_{$meta_key} filter to modify capabilities for all types. 
+			 *
 			 * The dynamic portions of the hook name, `$meta_key` and `$post_type`,
 			 * refer to the meta key passed to map_meta_cap() and the post type, respectively.
 			 *
@@ -284,8 +300,9 @@
 			 */
 			$allowed = apply_filters( "auth_post_{$post_type}_meta_{$meta_key}", $allowed, $meta_key, $post->ID, $user_id, $cap, $caps );
 
-			if ( ! $allowed )
+			if ( ! $allowed ) {
 				$caps[] = $cap;
+			}
 		} elseif ( $meta_key && is_protected_meta( $meta_key, 'post' ) ) {
 			$caps[] = $cap;
 		}