Sorry if I am intruding on your discussion, but I wanted to throw some thoughts out there.
I am trying to approach this whole Amoris Laetitia controversy as objectively and as open-minded as possible, so I too have been looking for good examples of situations where this debated exception might apply. I don’t know much at all about the topic, and had to get pretty creative, but here is one I came up with:
A Catholic woman is in an invalid second marriage, as she was unable to get her first marriage declared null. This second marriage produced young children that still live at home. She has a “reawakening” of her Catholic faith, and comes to realize that she is living in an objectively sinful situation and shouldn’t be taking communion until things are made right. Thus she tells her husband that she thinks they should live as brother and sister in accordance with Church teachings. The husband becomes enraged that she doesn’t view their marriage as valid (he is a “practicing Catholic” who goes to mass with her regularly, but still holds deeply sinful tendencies). Furthermore, he tells her that if he gets even the slightest hint that she doesn’t view their marriage as valid (such as her not taking communion), he will leave her, take the children and find another wife. In theory, the wife could stand up to her husband and trust that God will provide for her and protect the children, but after consulting with her priest, they determine that the risk of damage to the children is too high. It would be better for now that she continue taking communion and living as his wife, hoping that he will be repent and change (or if the situation is deemed abusive, she finds a safe way out of it)
Admittedly, the example above is complex, and situations like that may have never happened before. However, I suppose it is theoretically possible. If any situation similar to that did actually exist, it is doubtful that such a husband would care whether or not the wife to communion (he would probably only care that she lived as his wife in every other respect). She could therefore choose to abstain from taking communion and trust that God would bless her with grace by other means in response to her willingness to abide by the laws of the Church.
Apart from this one, I am struggling to come up with any examples that don’t get into extremely subjective territory. For example, someone could claim that their children would be significantly damaged (spiritually, emotionally or socially) by knowing that their parents were not taking communion because they were not validly married. How one determines that such damage would occur, I’m not too sure, but I suppose it is possible. The counter argument would probably be that many children would benefit by seeing the sacrifices their parents are making to abide by the law of the Church. So again, theoretically possible, but seems highly subjective and would require a more concrete situation to evaluate.
Anyway, those are my thoughts. I could be way off, but I find the topic intriguing and wanted to throw those out there for discussion.
God bless!