Language-Agnostic Properly-Tabbing Code Editors for Linux

R text editors for introductory statistics courses

Given that you don't have an major specific requirements (like an object browser), it's probably best to use what you're already using as much as possible. Something like Textpad is very simple and can do syntax highlighting.

Here are a few more pointers:

First of all, the R console that ships with Windows has it's own script editor. Just go File > New Script. It's very easy to use and you can execute code by highlighting it. If you just want something simple, I would stick with that.
I use Eclipse (with StatET) on Windows, and I have used it on a Mac too. It's great if you want an extensive IDE (syntax highlighting, integrated console, SVN, etc.) with a small learning curve.
JGR is also very good and platform independent.
Sciviews (which has Tinn-R) has several other options, including SciViews-K which is an R extension for Komodo.
Two others worth mentioning are Rattle and Rkward.
Emacs and VIM have a bigger learning curve, but they're also very powerful, especially if you're already using them for something else.

What's a good unix editor to use with SSH on a typical smart phone?

A decent ssh client should give you access to those keys. Even a vi user needs to have control key combinations.

a console code editor with CUA (ctrl-x ctrl-v ...) key bindings (unlike vi)

You could use emacs with CUA-mode.
You probably have to configure it further to form it to your liking.
There are lots of extensions for key-bindings and it has a pretty powerful extension mechanism. If you get over the initial surprise that its all in lisp you might actually like it.

Trying to launch an external editor from within a Go program

Apparently, you have to set Stdin, Stdout and Stderr on the Cmd object to os.Std(in|out|err). Like this (assuming that the object is called cmd):

cmd.Stdin = os.Stdin
cmd.Stdout = os.Stdout
cmd.Stderr = os.Stderr

Credit for solving this goes to the guys on #go-nuts on freenode.

How to Select Columns in Editors (Atom,Notepad++, Kate, VIM, Sublime, Textpad,etc) and IDEs (NetBeans, IntelliJ IDEA, Eclipse, Visual Studio, etc)

Notepad++, Visual Studio, and some others: Alt + drag.
vim: Ctrl + v or (bizarrely enough) Quad-click-drag. In windows: Ctrl + Q (since Ctrl + V is the standard for paste)