I think the answer is simple: If you allow non-ascii characters in a lisp, it would only "feel" right if the characters were fully programmable, as opposed to just adding a handful of extra characters. Lisp users don't like new features if they aren't fully programmable- You should be able to declare a new symbol in lisp code somehow and then be able to use it, IMHO. This, however, is non-trivial to implement (though I've had some ideas about this that I've been wanting to code up for years but haven't had time to do yet...)
By that I mean if you define a table library, you should be able to write code that allows the data of a table appear like a table, with a grid and everything, right within your code editor. That's what I would mean with "fully programmable"
When you say you want "characters to be fully programmable" does this mean that if you had "fully programmable characters" you'd be able to edit tables in your code editor as you describe, or are you making an analogy saying that you'd want characters to be fully programmable like these tables are fully programmable?
The former- I'm saying that if you're going to allow more characters, I'd want to go all the way and have an editor that is part of the "language definition" that supports arbitrary graphics and ui elements that is controllable through the language in a "lisp like" way and would allow code appearance to be 100% customizable right inside the code.
No, I think what people are getting at is... why does program source have to be represented by only ASCII text? After all, if code is data, an IDE is just a data editor, where that data happens to be code.
I think it has been shown many times throughout history that notation matters. In fact, the entire concept of Arc is based on this principle. Otherwise, Common Lisp would be suitable.
Why does it have to be ASCII? No reason, The simplest answer may just be that the language writer feels that adding UTF-8, or UTF-16, support would be a waste of their time, or is below them. As for programming IN the language, it becomes a matter of what is easy for the programmer to type. In a way, this whole thing is a matter of deciding what is the lowest common denominator that one wants to support.
