If you have a cat, then you may have learned why TP should not be oriented in such a way that a cat clawing at it could pull the entire roll off the reel.
You'd be surprised, Arnie, but I have heard some mighty passionate and mostly irrational arguments from both sides. (The thing I was most amazed at the first time I visited the UK in the mid-'70s was the "hygienic" TP that was basically like wax paper.)
If you have a cat, then you may have learned why TP should not be oriented in such a way that a cat clawing at it could pull the entire roll off the reel.
We have a cat and a dog and we'd not think of under.
Z is right about the passion, and I, too, remember hearing that it was the most controversial subject in Ann Landers' column.
Of course, I can't imagine anyone hanging it under, unless of course you can guarantee that your wall is sterile. Think of a McDonald's restaurant or an airport...really, you'd use toilet paper that has been in contact with the wall there? Ugh!