I get that they have a lot of JS devs and there's a big community but if they went with Ruby I would have been so much more inclined to stick with it. Performance-wise perhaps it would not have been better. Emacs it is for me.
I have a feeling that that's correct, but to the same degree that every great Perl, Ruby, and Python developer can write reasonable code in any of Perl, Ruby, and Python given good reference docs. The languages aren't really all that different if you take a macro view (and include lisps, static typed languages, etc).
Just in case you don't know about it. If you are looking for an editor written, and extensible, in (j)ruby then there is always http://redcareditor.com/
Project is dead but the program is a pretty fully-fledged text editor from what I have heard.