How does filing a chapter 7 case affect a person’s credit rating?

It will usually worsen it, if that is possible.  However, some financial institutions openly solicit business from persons who have recently filed under chapter 7, apparently because it will be at least 8 years before they can file another chapter 7 case.  If there are compelling reasons for filing a chapter 7 case that are not within the person’s control (such as an illness or injury), some credit rating agencies may take that into account in rating the person’s credit after filing.