Google should penalize sites that allow comment spam. Incentives are then clearly aligned, as the affected site has the power to fix its problem. Sites that can

Google should penalize sites that allow comment spam. Incentives are then clearly aligned, as the affected site has the power to fix its problem. Sites that can't afford to moderate their contents should just turn comments off. As mentioned in other comments, the changes described may just change the spam. Instead of linking to your own site, you instead link to sites ranked above yours.