That's crazy - the bot comment voting is something I've only just become aware of. Something happened on a post with a bounty on it. I've included a screenshot below. If you go to the guys account almost all his comments are voted on by the same people - resulting in similar payouts. I deduced it's in an attempt at scamming the bounty system.
There's a ton of these voting circles, you can report them on steem.chat
Think I'll do that. Thanks for the tip!