It's interesting. My husband and I have a huge mix as far as compatability goes... overall it's been challenging but very workable and we intend to work on our challenges. I am a Leo Sun, Taurus Moon and Sag rising and he is a Scorpio Sun, Aquarius Moon and Taurus rising. Our saving grace has been the fact that my Moon (and Mars) and his Ascendant conjunct one another, so there is a lot of understanding there... and my rising sign and his Moon sign sextile one another.
However, my mother in law is another story. She is also a Taurus Sun (which squares my Sun but conjuncts my Moon) but her Moon is in Capricorn (not sure what her rising sign is, no exact time of birth has been noted)... and my Moon and her Moon does trine one another. Though I do have compassion to some degree for the woman, and have forgiven her for a lot of the things that she has done to me...and I do understand where she is coming from.. but she is living at a low vibration and that in itself is repulsive. It's one thing if she wanted help but she refuses it. Even my husband has tried to help her and the thanks that he gets is her screaming at him for 3 days! I guess because of the fact that her Moon and Sun trine one another, she is even more resistant to change and has no sense of spirituality what so ever. Even though she is miserable, she is too comfortable in her state... probably due to her Moon and Sun trine (and being earth signs). Even though my Moon and her Moon trine one another (which is why I understand where she is coming from), I cannot be around the woman! From what I see in the chart I was best able to come up with for her, there is a lot more friction than ease. Anyway my point is, the Moon sign will help to a degree as far as compatibility goes.. if anything like mentioned above it will help you understand where the other is coming from if your Moon is compatible with theirs.. but it doesn't mean you will necessarily get along.