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.
4 lines of code could catch this.
4 lines of code could catch this.
And now Reddit has made it possible to hide your post history.
Probably because of this exact issue.
That's using reddit's own site, of course there are other methods like Google dorks.
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.