The better question is what percentage of _printers_ could handle arbitrary overlap, and I think the answer is, all of them. It's just a head striking paper,

The better question is what percentage of _printers_ could handle arbitrary overlap, and I think the answer is, all of them. It's just a head striking paper, backspace and strike twice is always an option. Printers were fare more common than hardware terminals for most of the initial history of computing.