If someone leaves an insightful comment on a post and it's immediately cloned, the post author and other readers have an additional barrier in determining who they should reply to for a constructive discussion.
This is one of the downsides of comment plagiarism. It is very funny since comments are a way of building relationship with the author. Gaming it for short term value won't help anyone in the long run
Sure it won't help anyone in the long term but do you really think that someone who does that thinks about the long term?