An accounts "history" and "reputation" will be tied to each site. A liberal who posts regularly on echo chambers on both sides of the aisle will have a middle of the road reputation. On Fox news for example you'd see next to their comments:
FoxNews.com Rep: -123 Global Rep: 38
A high global rep is due to the high score posting comments on WashingtonPost articles. Where you would see:
WashPost.com Rep: 161 Global Rep: 38
I'd expect someone with a reputation of 0 to be an honest individual gaining views on both sides of an argument. Someone with a global rep of -1833 is probably a troll or someone who doesn't interact with "like-minded" people, which could of course be seen by looking at the history of where the reputation came from.
You as a consumer, would most likely flag site reps to show on all pages, so maybe you on every site you visit would see a users reputation like so regardless of the site you are on:
Current Site Rep: 3 FoxNews.com Rep: 283 WashPost.com Rep: -87 Global Rep: 221
And you could, of course, dig into their history of reputation, and even Hide/star particular users who you notice are trolls/note-worthy to you personally.