You left out a further explicit mention of conditional requests: > Advised (via Retry-After header) to come back in one day since they are unwilling or unable

You left out a further explicit mention of conditional requests: > Advised (via Retry-After header) to come back in one day since they are unwilling or unable to do conditional requests. But I think it's still unarguable that the post doesn't explicitly mention If-Modified-Since, which it's not obliged to do, but the mention of it here could be helpful to someone. So why fuss?