Unfortunately, "support for most platforms" tends to result in the kind of user experience that I described above. There's something comedic about millions of lines of compiled Chromium failing to handle the Control modifier on Linux.

I can't really blame them (Linux, like every nix, does something unique at the tty level that breaks reasonable assumptions), and I'm sure it'll get a lot worse once they try to run their JS bindings over the pty/tty subsystem of something like Solaris.

I'd say a browser introduces a non-negligable cost.

Agreed, though this is a situation that should be improved if the industry wants everyone using browsers for everything.