There is a user
Thank you for not identifying this user publicly.
Are the algorithms that block users from contributing endless low-quality answers set by the corporation?
Yes. There are a few different “bans,” which are discussed more on the network-wide Meta in various posts. Some low-quality contributors get “throttled,” so that they can only post one question (or answer) per week. For questions, other users are just blocked until their “question record” rises above some threshold. The question record counts every question asked worth +1, but then questions which have negative score, are closed, or have been deleted get -1 for each status. This means that deleting a downvoted and/or closed question makes your posting history “worse,” from the perspective of running up against quality restrictions.
There is a similar set of automatic thresholds for answers. However, some of the automatic bans also account for user reputation, and may not apply to high-reputation users.
[I’m writing this summary without digging though the various Metas to confirm details. If I’ve gotten something wrong, please link to an authoritative post and I’ll fix it.]
Can moderators step in and apply their own judgement?
Yes. Moderators can and do suspend users with a pattern of low-quality contributions. If you think you have identified such a user, please flag one of their posts.
The range of net votes on individual answers is from -9 to +1.
When the moderator team is discussing such a user, there are a few things like this that we usually discuss.
Is the user in question an especially prolific poster? At some point I wrote a SEDE query to identify such prolific users. Somebody who is posting several times a day (which, recently, is nobody) is much more likely to attract site attention than somebody who is only dropping by every few weeks.
Prolific posters pose potential problems whether their answers are high-quality or not. For instance, I happen to be an astounding genius who knows everything about physics and explains with stunning clarity. (sarcasm emoji) But if I were to answer every question, so that the site turned into “rob’s awesome physics blog,” that would be weird and bad for the community.
Are the posts in question recently low-quality? People come here to learn, which starts off with not knowing things. Several users have responded to feedback (from the moderators, from the community, or both) about low-quality posts by becoming better writers.
Are the posts in question a distraction to the community? We’ve had users in the past who have posted low-quality contributions and then fought about them in comments, in chat, on meta, leading to bad feelings all round. We also have users who attract downvotes, but aren’t disruptive.
answered almost 90 questions and gotten, if I added correctly, a net -76 votes … these low-quality answers have already “reached” 20,000 people
There’s nobody in the SEDE query linked above with a negative mean score on their recent answers. The “reached 20k people” metric works out to about 200 viewers per answer … but I think that counts everybody who loads a page containing an answer, whether they scroll to that answer or not. I wouldn’t take that number seriously.
The next time you notice a bad post by this user, you might raise a flag and point out that it’s part of a pattern of low-quality contributions. Flag histories accumulate, and we may or may not take action immediately, and our response may or may not be visible to you.