Gregory's Server@b0rk I don't think that it is all that obvious that readline is not part of the driver. Providing kernel-level line editing basically was a necessity in the 16bit era, but when machines got more powerful, providing these things in user mode became more common.
What that also meant is that there was no single line editing system, but each user-mode program could (and needed) to provide its own. GNU readline, albeit popular, was really hindered by its license.
@b0rk With a user-mode line editor, it is only the control characters that generate interrupts which require driver support, and modern implementations don't even need to rely on the driver to send signals (i.e. they treat Ctrl-C like any other character and send a SIGINT if they want to).