I do disagree on this.
See here after:
$ cd /tmp/
$ mcedit test.txt
/adding some text, then hit F2 to save, then F10 to quit, then:
$ cat test.txt
Hello World!
> Hello!
I can do it, so should you ?
Maybe were you talking about the editor when you are inside mc ?
I just tried I can do it too. Open mc (in /tmp for instance), get the selection on top, on "..", hit F2 then go up to '@' "Do something on the current file", once there you can type a command line, type "mcedit text2.txt", don't mind about the warning and edit your file. Once done, hit F2 to save, then F10 to quit: you have a new file.