It sounds like the Nords have a "live and let live" attitude when it comes to six, going by how the Priesthood of Mara deals with marriage and how the Priestesses of Dibella deal with six.
Nords care only about
who you are, not
who you do. You can be a total player and bed every handsome dude in town, male or female, but so long as you're honorable, brave, and an overall upstanding citizen, no one's going to bat an eyelash.
This is an attitude shared by the Japanese and Greco-Romans of old. So long as men (noblemen granted, but bear with me) fulfilled their duties as fathers and husbands, they could sleep with whoever they wanted. They could hire consorts, have multiple wives, have more "private" relationships with other men etc. This is probably true for Skyrim's society as a whole (sans the polygamy) regardless of six or position, but far more romantic, intense, and egalitarian.
TL:DR; Nords don't give a damn on what gender you like. Just be a good person.
Gameplay-wise, marriage isn't the prime feature of the game. Relationships in general aren't part of Dovakin's story. Still, I'd like to see some same-six couples, which lorewise do exist as far as I'm concerned, but it's not an aspect that takes center stage. I honestly think that the marriage system was rushed. Either way, at least we have an idea now on how one of Tamriel's race treats an issue that shouldn't be an issue in the first place
