Not to be too tangential but if google, valve, facebook, anyone wanted to crack down on spam, the way to do this is to USE HUMANS. Set up an office and hire a hundred or so people who sift through content and mark up what is and is not crap. If [GIANT COMPANY] doesn't want to fork out a sub 100k salary to a few hundred (or even a thousand) content mods, which is really not too much in the grand scheme of things, then they can charge people to get their site reviewed before listing it. If each website had to pay between 100 and 1000 dollars to get a ranking on google, that would cut down on spam quite a bit. Same thing with any of these giant companies.
The big problem is that you need to address the human element of having a staff of moderators. Make sure they have health care. Make sure they behave professionally. Have a hierarchy of oversight so that decisions are checked and possibly appealed. Its a business. But none of these arrogant monopolies feel like shelling out the dough and time to design such a system even though it would provide the highest quality results anyone has ever produced.
We should be sus of human error, but because its an "alogrithm" we aren't supposed to be sus of errors, nepotism and bad arbitrary decisions? And if the algorithm decides that our game is only worth a few hundred dollars, its great that there is no way to appeal?
No that's me speculating about why they wouldn't wanna be public about something like that. Most people probably feel it's more acceptable that everyone's subject to the same blind machine decisions than some guy looking at your game and dealing out ranking scores based on whatever is happening in his particular head in that particular moment.
But the point about opaque algorithms: it's probably an unfortunate inevitable reality with search rankings. There used to be an arms race between SEO spam sites and google before google just gave up. That war would have been lost before it started if the algorithms had been public.