This is analogous to SEO, but rather more insidious and sneaky. You can spot SEO blogspam from a mile away. You don't know if a Reddit user is a real person, a bot, or a company's representative.
I'd wager you could do a lot to influence public opinion with just an upvote ring, without the botted accounts actually needing to post messages.
That was your first mistake, the defaults are cesspools full of karma farming bots. Nobody goes to those for advice.
I'm sure it happens a lot regardless, but the vast majority of content in those is still just from regular people. You can tell by the information posted as it tends to be more or less truthful and useful. Once it stops being that it'll be obvious enough. Like when Russian bots invade your average Ukraine related r/worldnews post.
That's the magic of Reddit, 4Chan and every other cesspool where any niche is only a slight URL change away from any other niche.
It's trivially easy to add niche subs 2, 3 and 4 to the list of places that you target.
2) You can tune these systems to be indistinguishable from a flesh and blood product fanboy at first glance. Not all spammers drop the same comments mentioning their product everywhere. You can dilute it with meaningless AI generated banter so the mod has to scroll through a couple pages and connect the dots before deciding whether you're a bot or just an idiot who happens to like some product.
Take r/mechanicalkeyboards for example, arguably a niche community. The enthusiasts there are very motivated to buy new things and are willing to pay quite a lot of money for them. Place a few of your bots there to promote your artisan keycaps and watch people pay top bucks for them.
Well, if "nobody" goes there, how are the bots able to farm karma? Who's giving them the views and upvotes?
I guarantee you anything that's the "default" is being visited by many, many casual visitors, people not "in the know", and people who don't recognize karma farming bots for what they are.
Also how the fuck "Building a hobby-shelter while camping in Kelowna" or some random funny pictures is "astroturfing"?
I just headed over to one of the popular subreddits and randomly picked an account that posted a top meme
https://www.reddit.com/user/esberat/submitted/
The account has 8 million post karma and every single post it submits to a subreddit ends up on the front page of Reddit... without fail.
The account isn't a mod of any of those subs, but they're clearly using upvote manipulation to get every single one of their posts to the front page.