Ligatures in your editor don't change the underlying, code they just change the presentation of that code when you're viewing it. While a ligature supporting font may show you ≥, the underlying source file still contains the distinct characters >=
yes "up to a point lord copper". What what happens when this code is copy pasted, moved between machines in different countries or edited in multiple different editors you can get bizarre problems.
Even moveing excel between countries gets some very strange changes Eg changing diacritical's but they look very very similar.
Absolutely nothing happens. Ligatures are a feature of fonts and font rendering engines. They do not affect the character codes. If you copy-paste from an editor configured with one of these fonts to an editor that isn't, you'll simply see the ordinary characters, because that's what was in memory the entire time.
