MLCers generally do not listen to others when it comes to what they are doing. As Cali pointed out, they do not think that there is anything wrong w/them, therefore, they tune others out. In fact, some will even think that we, the LBS, put people up to trying to convince them to return home and to the relationship. People who attempt to help are generally then shut out like the spouse. The more we try to help/reason w/them the more determined they are to do what they want and the same applies to others as well.
The best thing that you, as the spouse, and others can do is be a safe place for them to land and that means listen, affirm and do not judge them. Part of their complaint is controlling and manipulating them and that's what they think they hear if others step in and try to talk to them.
Also, many of them will do to counseling and come away w/the idea that divorce is the answer, when, in fact, the counselor didn't suggest it at all.
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.
