protected function conforms_to_letters_policy( Token $token, $policy ) {
		return $this->check_policy(
			$token,
			$policy,
			self::ALLOW_ALL_LETTERS,
			self::REQUIRE_ALL_LETTERS,
			self::NO_ALL_LETTERS,
			function( $value ) {
				return \preg_replace( self::_RE_HTML_LETTER_CONNECTORS, '', $value );
			}
		);
	}