AFAICT, even in 2.0 it's still important for Japanese users who may useBozhidar Batsov <bozhidar@batsov.com> writes:
> Since Ruby 1.8 reached end of life in the summer and most projects these days use Ruby 2.0 (which
> assumes source files use utf8 by default) having `ruby-insert-encoding-magic-comment’ doesn’t make
> much sense. Most people just disable it anyways, so why not have it disabled by default?
an encoding other than UTF-8.
Disabling the addition of magic comment when UTF-8 is used should be
done via adding '(utf-8 . nil) to `ruby-encoding-map', and even that I
can't support personally since our team, at work, is still on 1.9.3.
Also see http://lists.gnu.org/archive/html/emacs-devel/2013-10/msg00236.html