I can imagine good enough AI being able to spot truth even better than what humans do - by veryfing sites and commenters with sources of real information to estimate their credibility.
E.g. in a theme similar to Page Rank, you could have an AI that has some sites as a source of objective truth (Wikipedia, science journals, reputable sources of news etc), and then use that as a basis of estimating trustworthiness of a material.
Also, AI could find, for a given subject, opposing opinions, and estimate which ones are possibly fake, and which ones are real.
In essence - do what current fact-checkers do, but for every single website and comment in existence.