wp-includes/ms-functions.php:2291Determines whether a user is marked as a spammer, based on user login.
$userstring|WP_Useroptionalnullboolfunction is_user_spammy( $user = null ) { if ( ! ( $user instanceof WP_User ) ) { if ( $user ) { $user = get_user_by( 'login', $user ); } else { $user = wp_get_current_user(); } } return $user && isset( $user->spam ) && 1 == $user->spam;}Introduced in MU (3.0.0). Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
src/wp-includes/ms-functions.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.