True, the laptop and compact apple keyboard lack a right control. I've found that I use the right option key infrequently and use Karabiner to remap the option to control. It definitely helps with the RSI, and makes switching to someone else's machine frustrating :)
Why would you remap the left option key to ctrl when you already have two left ctrl keys (caps and original ctrl) ? I do set the right option key to ctrl but only in iterm and emacs.
Because I'm bad at writing! (I meant right-option)
You have no idea what I am doing with the esc, capslock, and control keys on the left side of my keyboard, but none of them are default.
On the right however I'm just trying to make sure I get a forward delete somewhere. In fact using Karabiner or Seil, the right shift is now shift if pressed as a modifier, but forward delete if pressed alone.
For me, when recently trying to remap the left-shift key I found out that it was not a problem for the supposed best practice of using it for C-g/x/c etc, but that instead I had been using a worse practice for typing ":" or """ when the wrong characters turned up al over the place.
Anyway, I suppose the left option key would be pretty good to map to control for emacs, since it's rarely more needed than the right option key.