Doesn't work and alters WP core files permanently

After installing this plugin, I found it did not work. In addition once I deactivated and deleted it, the changes remained on my site because the plugin actually rewrites functions form the core files!!

If it’s too late an you’ve already used this, I’m posting the core files it modifies below. I simply restored these files from a clean WP download.

modifies: wp-includes/comment-template.php
modifies: wp-includes/author-template.php
modifies: wp-comments-post.php
modifies: wp-admin/edit-form-advanced.php
modifies: wp-admin/post.php