I haven't seen much information about the specifics of how report weights work.
So it takes a certain number of reports for a person to even be reviewed. So to me the most logical way to do it would be to have reports remain neutral until the person you reported gets reviewed at which point it would change to either invalid or valid.
I'm also not sure how important report weights even are anymore. It was extremely important back in the day because the system heavily relied on report volume for accuracy. If the average person gets reported in say 5% of games then the further you get over that the more confidence that you can have that the person is doing something wrong. Now it seems like the only real purpose for report weights is to cut costs by avoiding scans based on frivolous reports.