The catch is, if I try to work with code relying on special stuff, and I don't have your special font, or special extension, etc. your code will look terrible.

The catch is, if I try to work with code relying on special stuff, and I don't have your special font, or special extension, etc. your code will look terrible. Consider for any of these ideas (and the idea of various fonts) just how well it would work for the masses. Consider the mess if someone works on an open source project and checks in a bunch of code formatted for this. Which is why I guess I'd see any kind of "fancy" spacing or even proportional fonts to be a real problem in an organization or structure where potentially many people, or new people over time, will have to work with the code.