Is Yahoo aware how many people no longer bother clicking on their news articles without comments? Doesn't that hurt their ratings?

Yahoo's an aggregator. They gather in stories from many sites. If you look closely at the top of each page, you'll see that most stories are not actually generated by Yahoo.

You can find those stories on their original sites, where they often have comments sections..

The sources they use are generic third party ones anyways before and after. They have always been garbage. They're simply too lazy to moderate the comments in return for the ad revenue. 

No one but right wing whiners ever bothered with the comments, who cares about the uninformed opinions of those people

Probably. But you've all been coming on here to whine about the lack of comments for the best part of year, so that evens everything out.

The people who commented on Yahoo articles only read the headline and went straight to the comments. The people who read the articles still read them.