If it's not already on your bureau, and you pay it, I don't think they'll then put a negative (or positive, for that matter) remark on your bureau. It'll just stay incognito.
If you don't feel morally obligated, there is a form letter that someone can link you to that will invite them to launch a civil claim action (that you can successfully defend based on the statute of limitations) and remind them that all contact is to cease unless it is related to the court case.