It's so painfully obvious too. On my local subreddit: "what's the best ice cream shop in $CITY?" Check their post history, one "lol" on a cat pic on /r/aww 8 months ago.
The funny thing about that is it's extremely simple to bypass. On old or new reddit, search 'author:example' to find posts by /u/example. Or to see both comments and posts, on new reddit go to the user profile and do blank search like a single space character.
That's using reddit's own site, of course there are other methods like Google dorks.
Well that and some moderators of large subreddits like to ban people based on participation in other subreddits that “disagree” with whatever flavor echo chamber the moderator happens to live in.
And yet I suspect it's super effective, because of the powerful illusion of it being real people.
There's the classic search "hack" of adding site:reddit.com to any product recommendation search, to find "real" recommendations.
Most of the time this is going to find 5-10 posts, each with only a dozen comments and a dozen up-votes. And yet it feels do much more real than whatever at the top of Google that many people will trust these reviews.
4 lines of code could catch this.