The Bitcoin protocol isn't encrypted (it can't be, nodes have no identities in the network), and doesn't attempt to mask itself in any way. An ISP can absolutel

The Bitcoin protocol isn't encrypted (it can't be, nodes have no identities in the network), and doesn't attempt to mask itself in any way. An ISP can absolutely log every transaction relayed by their customers... of course, it's still impossible to determine whether that person actually created that transaction