Think of the negative effects. This would promote posting correction-bait.
You already get a +>1 if your comment is valid and improves the discussion.
Whats the goal?
We want a lively community of discussion.
How does giving you karma points as the father (or grandfather) of a discussion add to that?
I view points first as a method to connect readers to great material which further improves the knowledge of the community, and a side benefit is they can help a commenter/poster further connect to the community and get an understanding of their value.