If I understand the liking system correctly, the purpose of upvoting a post/comment is to show support for it. Take this line from the Orion faq. "Orion can still have [a feature], if the feature request on orionfeedback.org garners enough support (upvotes)"
It's possible for a comment under to disagree with the original post. Someone could agree with the disagreeing comment and like it. This results in the original post being upvoted automatically, implying support for the post when the person actually disagreed with it and only agreed with the opposing comment.
My suggestion would be to not automatically like a post if a comment in that post is liked.