Not that I'm defending the practice (and certainly don't have enough skin in the social media game to do it myself), but it is extremely common to have alts upvote/repost each other on social networks, or downvote brigade someone when you're losing an internet argument.

I doubt that even 1% of people using Reddit are using alts to upvote themselves or downvote brigade others. If you have any data to the contrary I'd be happy to hear it.

It's still a solid sign of a sad life.

Or a small business, but I wonder how much money there is in that.

> Or a small business, but I wonder how much money there is in that.

They call it "hustling" and "growth hacking", and I suppose there might be good ROI on this when you're just starting up and trying to do some "organic advertising" in a niche community/subreddit. Those couple extra upvotes may be the difference between drowning unnoticed vs. staying on the front page long enough to gather initial interest, and spark a discussion that keeps it up for a day or more.

I still believe it's unethical behavior, though.

For some values of "extremely common", because I'm pretty sure most people don't have the patience and energy to do bullshit like that. But a small fraction of people do it a lot.

Or manufacture controversy for engagement? For example, I posted the 4 comments above all from accounts I own (/s)

This is actually more useful to me today. If you want a good, well-researched answer to a question from an expert, you are much more likely to get it on reddit if there are a few "idiots" with wrong answers available for that person to dunk on.

>You're running a one-person troll farm? Please reconsider your choices in life.

how else do journalists write this articles on internet hate mobs?

Infamously u/Unidan, a very popular figure on r/askscience posting high-quality answers to biology questions, was banned from Reddit when it was revealed that he used alt accounts to upvote himself/downvote those he was arguing against. Such a shame that he felt the need to resort to something so stupid.

It wasn't stupid. It's quite likely that he would have been stuck down in the noise like so many other high quality Reddit posters except that he realized early on that just a handful of early upvotes makes all of the difference to Reddit's algorithm. The Reddit algorithm is seemingly designed to snowball content, so if you want to rake in the worthless karma reliably you need alts.

I’m not so sure. Many other "household names" on askscience seem to be highly upvoted, apparently without shenanigans (but who knows?!) Even I have several 1000+ karma answers there, and many more 100+ ones and I’m a nobody. There’s also simply not much competition on askscience! If you’re consistently able to write good, a-few-paragraph answers to questions in a particular field, and are also available for discussion and followup questions, it’s not that difficult to become commonly recognized there without having to compete against others.

I think you may be underestimating the effect of this. With time, you can get several 1000-karma posts, but I bet you also have a bunch of 1-10 point things. Literally every comment and post that u/Unidan made had 100+ upvotes. He could comment about birds on a quantum physics page and get 100's of upvotes. As a result, everywhere he posted, people would see all of his comments "organically," and that kept all of his posts outside of the 1-karma hell that consumes a lot of amazing insight. That's the effect of bot usage.