That's basically how astroturfing works though. "Marketing companies" have rotation of accounts that they use to create discussions to make it sound real. The easy ones to spot (again, i'm just a messenger here, but been paying more attention since I've been told about it during drunken rants) is when a reply-comment is asking a very simple follow up question regarding a product review, which can be easily Googled, so the OP would respond back with even more positive reviews. It's fun sometimes to spot it and go into account's history, and sometimes it becomes extremely obvious from just the subs they frequent.
The other couple fun ones that are easy to spot - someone asks for a recommendation, and a comment is a list of 3+ brands to make it sound "organic". You go into the history of the account, and you can see they always include one specific brand name in every list they suggest with 4-5 months in between posts. Or someone asks for a recommendation (brand themselves), then there's a response from a random person suggesting a brand that is extremely niche, and the OP a few days later comments back saying "i tried this, and this is amazing!".
My guess is, most of it is a "long game", as Reddit et al. is extremely lurker-heavy. I could see SEO companies setting up shops and having different tactics to play the game. The other problem is, since every company is doing it, you will get a "great product from Reddit recommendations", as those great companies also have to do it. But it's just a gamble at that point. As much as I'm not a fan of them, I tend to stick with wirecutter / consumerreports as my "starting point" of the research, where it applies. Not the best, but I feel less tricked than going through Reddit.