Barleywine
If we're talking touching and not sharing, I expect my sitters to handle, shuffle and cut the deck. Sharing I assumed meant letting someone else read with it.
I'd let someone else use a deck that I have but don't use. Otherwise, nope nope nope. No touchy my cards, much less reading with them. I'm possessive like that.
I'd also be uncomfortable using someone else's cards, because I 'broke' someone's deck once. But I would happily buy a used deck, because that's not sharing.
How do you "break" a deck? Just curious.