Any trad priest of any background will give the same answer on this, since it is exactly the answer given in any book of moral theology. A person can attend a non-Catholic wedding or funeral if necessary for social purposes, i.e. if the person getting married/buried is a family member or friend. While attending such a ceremony, someone must not participate actively in the religious activities, but only remain passive, such as by sitting through the whole thing in the back of the church.
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A Novus Ordo service is a non-Catholic ceremony, and thus comes under the above rule.
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Anyone saying the Novus Ordo is some exception, such that it would still be a sin even to be passively present and not participating at a wedding or funeral, is incorrect and should be ignored.
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You don't have to trust me on this. You can ask any trad priest you want and you'll hear the same thing.