Fitch Ratings has combined its criteria for rating residential mortgage originators and third-party due diligence involved in non-agency MBS issuance. The company said the move does not involve any material changes to its rating methodology. All originators contributing loans to non-agency MBS rated by Fitch are subject to periodic reviews by the rating service that can lead to adjustments in loss estimates for the deals or even cause the company not to rate a transaction at all. The rating service will look at the performance history of the loan originator, including repurchase requests...