Please settle this disagreement between me and my wife -- let's get between the sheets

Nah, it has never been the province of formal etiquette to rule on trivial private matters like that. Emily Post’s 1922 Book of Etiquette, for example, specifies lavatory amenities for guests like providing fresh soap and hand towels, but not the orientation of the toilet paper.

And Miss Manners was pointing out that toilet paper direction is not an etiquette issue as far back as 1987:

Hmmm, it strikes me as a shallow and artificial identification of “etiquette” with gratuitous snobbish snootiness.

Certainly, there are some people who claim the authority of “etiquette” (or “manners”, for that matter) merely as a justification for gratuitous snobbish snootiness, but that doesn’t mean that anybody else has to agree with them. Ultimately, etiquette systems are fundamentally about creating a reasonable set of standard default social conventions, so everybody can avoid feeling inferior.