Pleasure reading the threads on the subject. It was a scientific experiment and results were quite interesting.
There's a photo of me testing the dispersion of a paper in water.

I'm a chemist and I did wonder myself about added vitamins in toilet paper. I don't know the reason but it may be a genuine one. Vitamin E is an antioxidant - often found in toiletries and creams for the skin. But why in toilet paper? Possibly to inhibit reabsorption of toxic waste products? or to oxidise toxic waste products into something less toxic.

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Derek Robson
Advantica Limited
Loughborough