Child Themes and WP-Includes

I need to edit something in the wp-includes\comment-template.php folder, but i’m using the parent/child theme relationship. I don’t want to edit anything that will be overriden when the parent theme updates. I know that to override all the stuff in the wp-content/themes/parent-theme-folder i create a child theme in a folder at wp-content/themes/child-theme-folder. But what do I do if I want to override something in the wp-includes\comment-template.php???

Specifically, I want to edit where it says “Leave A Reply” in the comments area to something like “Leave A Comment About This Business”.

Please advise what I should do, that will protect from parent theme updates overriding my changes???? Thanks in advance.