Can't speak for WaPo but the New York Times comments sections are absolutely dominated by a handful of designated 'top commenters' who rush to post on any major story. Sometimes their comments are good, but then there's the guy who writes a poem every single time, or 'Socrates' who posts the same cookie-cutter 'blame-the-GOP-all-the-way-back-to-bush' comment with the most dramatic rhetoric possible, trolling for like…
Then the hack: this is a newspaper. They have no reason to be fair. Give community moderators super-credibility. So they can upvote people and not just give their comment visibility, but by upvoting they incidentally give them credibility for future comments. And in turn, those commenters' upvotes are more powerful as well, thanks to the credibility lent by the community mods.
It creates an echo-chamber, of course... but ultimately, that's what people want.