I mean, of course it is. Marketing companies have long since realized that they can have far more effective advertising by acting like humans, and that people will take a recommendation from another person more serious than a random ad. Propagandists have had the same realization.

If you consider how fast you can generate huge amount of random comments, it's basically a no-brainer that huge amounts of online comments are online generated.

The only real throttle is the social media platform itself, and how well it protects against fake accounts. I don't know how motivated Reddit really is at stopping them (engagement is engagement), and a quick check on Github shows that there are a bunch of readily available solvers for 4chans captchas.