Half-link chains are bad. They stretch out easily because a half link will stretch a fraction of a millimeter and this gets multiplied for each link so a chain can stretch quite a bit. However a chain with single half link will not stretch noticeably different than a chain without the half-link because the amount that a single half-link can stretch is tiny. I think people hear "half-link chains are bad" and they think that means "half-links are bad".