I bet not even E-harmony thinks to ask about this one. I've never heard of it coming up in premarital counseling.
Nonetheless, it's an important question.
How do you eat your grapefruit?
See, I eat grapefruit the proper way, which is to cut it in half, put it in a bowl, sprinkle with salt (OK, so nobody else does this. But it really does taste better.), scoop out the innards one bite at a time, and then squeeze the juice drop by drop into your spoon. A luxurious breakfast experience.
DOB eats grapefruit like an orange: peel, section, eat.
We both refuse to budge.
The trouble is, grapefruit is a two-serving fruit. Thus, instead of sharing a single grapefruit per breakfast, we wind up always having these odd (and bulky) containers with two differently-shaped halves of grapefruit in the fridge. These tend to dry out and not be so tasty the second time around.
The obvious solution would be to each train a duckling to our preference in grapefruit consumption, but so far they have little interest in grapefruit, and ask for a banana or orange instead.
Another area of compatibility I forgot to check was blood type. If only DOB had RH negative blood, I wouldn't have to get Rhogam shots with every pregnancy. I can't convince him to change that, either.
I think we shall survive nonetheless.