Thank you for the feedback.
> You might want to check that point and mark are both inside the src block. Otherwise, the results are unpredictable.
You are right, I've updated the patch.
> ess-mode, python-mode, sh-mode and octave-mode already provide this
capability (and a lot more) for R, python, shell scripts, octave/matlab
and some other languages from the edit buffer.
I understand that. My idea is to avoid the need to C-c ' back and forth. Actually that's a problem I have with org-babel; I usually find myself coding inside the src block and losing many of the major mode functionalities; switching to the edit buffer often seem too much of a hassle. Any tips about how to get more major-mode functionalities inside the src-block? Or should I develop the muscle memory to switch back and forth to the edit buffer all the time?
> `org-babel-demarcate-block' gives the user the ability to break up src
blocks into smaller pieces so they can be run independently.