You can actually see it right there on your own comment. It's the guy who gave it the first (and only) downvote. His steam power is over 12000 and his reputation is 45; so all those with lower reputation and lower steam power are vulnerable. There has been a suggestion that declining rewards would make one's reputation immune from downvoting - well, that doesn't appear to be working too well (one downvote from that behemoth bully = hidden comment and minus 1.5 to the reputation.)

P.S. Now he gave me 100% downvote for this comment, so my reputation is down to 23. If you could upvote both comments that he downvoted to offset the damage a little bit - I'll appreciate. Thanks.