you should read @steemcleaners post, Abuse Guide - 2017 Update

Comment Spam

• 10 or more generic comments per day that are not in response to a question posed by the post or comment. “Thanks”, “Great Post!”, “Nice”, “Follow me”, etc
• Commenting on old posts to hide self up-votes or a voting trail.
• Copy/Paste comments that serve no purpose or the purpose is self promotion.
• Comments that inform the contributor that they have been up upvoted, resteemed, or flagged when the curator does not actually upvote, resteem, or flag the post.
• Unsolicited and off topic referral links.