Let's face it, they already had it on some of the big default subs as well.
I went though a phase of bot hunting, and it was not unusual to find comment chains of 3 bots replying to each other near the top of big threads, sometimes with a hapless human or two in the mix.
They use snippets of comments from downthread (and usually downvote their "donor" comments to lower visibility) so it seems kind of organic. Sometimes they use a thesaurus or something and re word it somewhat.
What was really sad was when you'd see a human writing screeds of long arguments in reply to them.