What happens to non-reporters if they refuse to answer the call of the court?
Actually, same thing, just quicker. Most John Q Publics don't have access to top level law firms and this dance of the seven veils about reporter priviledge, which simply does not exist at Fed level. Some states grant a form of it, but if a federal judge asks for a response, you can: answer; plead the Fifth perjuriously; commit direct perjury; or keep silent and sit in jail for the life of the grand jury, usually about six months.