Perfect example I found the other day... the main post is clearly a bot, and all the replies are bots pretending to be users too.

Reddit USED to be amazing for finding recommendations for products/services but these days it’s just another bot-filled and paid-content dumping ground like the Google search results.

https://www.reddit.com/user/amily95/comments/fkm1rn/how_to_c...

Sometimes it's obvious - the same user posting/commenting the same link across many related subs with very low signal and no other posting or commenting activity.

Or you see the same link and comment/post text posted by many different users.

But this is just low-effort marketing. There's a lot of content that is relevant but also marketing. Burger/chicken restaurant twitter account screenshots getting posted to a default sub, for example.

as others said, it can be obvious if one account is used to share the same sentiment.

one other obvious one I've seen is when batches of similar posts for recommendations in category "X" have each received a reply, usually days/weeks after the original submission, all from different users, posted around the same time, recommending the same product