Even Worse, on MacOS when I have a file called "Foo.c" and I 'emacs -nw foo.c' from the command line, it happily opens the file. And then when I save , it silently overwrites it as "foo.c". And suddenly nothing else works on "Foo.c".

"downloads? I've never met that man before in my life!"

for a good reason

Not in Fish shell though 😁

put the following line in your bashrc
shopt -s cdspell