A lot of news sites allow voting without being logged in, as well as in the comment sections.

Business Insider, the largest business site, allows it (Quantcast #235).

It's premised on the notion that for 99.999% of people, they're not going to bother going through any amount of hassle to bolster votes artificially. It works, it's not worth the time or effort to game content and comments that are modest in traffic and throw-away in nature. The only way it's worth gaming, is on front pages like Reddit where there's a massive simultaneous concentration of traffic.