Not so subtle, but user CANWorkSmart seems to have created a bunch of shills to comment on his (now dead) post at https://news.ycombinator.com/item?id=3010356.

Might be worth it for a mod to kill them off...

edit: the '-----' appears in place of the 'reply' link when the post can't be replied to (in this case because the submission is dead?).