You keep the karma you've already received, but the project creator submitted the original post and also included the blog post in the comments (after it was too late to change the post URL) and we always prefer to give precedence to the person who submitted the first post about a topic. It's not personal or unusual, it's the way we've moderated HN for years.

Could you explain to me what is the appeal of chasing karma? I understand it at the beginning, when it unlocks features, but not after that.