I'm going to get grief for this, but I've never realistically seen them as having an open marriage. When even Blitzo describes their marriage as "boring-as-fuck monogamy," and if there's one person who would know as much as they do if they swing and have zero inhibition talking about it, it's him...yeah, nah.
Never said it doesn't make for a fun "what if," though. Moxxie is fun to ship with pretty much anybody, and from what I've seen, there's a general agreement of that.
Base +6, Macharius41 +6, Gamr13 +6, Rail vehicle fan +6, Urolo +6, Kitagawa84 +6, Qwertius +19, hon. +6, GodlessaWarrior +5