Replace text in Firefox, Pages, Terminal, BBEdit I have a MacBook Pro running the latest Sierra.

I often find myself wanting to type I²C and have created System Preferences/Keyboard/Text to replace I2C. I can't seem to get this to work in any program (Firefox, Pages, Terminal, BBEdit).

The inbuilt omw doesn't seem to work either.

Is there any trick I am missing? I have set "Correct spelling automatically" and selected "Check my spelling as I type", which works for normal spelling errors.
The specific parameter is Substitutions > Text Replacement, which isn't actually in System prefs at all.  

It's usually in the View menu of individual apps &amp; as far as I'm aware needs to be specifically enabled wherever it appears.

Apps that don't have that menu item won't do replacement. BBEdit is one of those. Most Apple apps have it, but not Terminal.