Formatting shouldn't be hidden from the scripter. It's simply a bad idea. Syntax highlighting which somehow differentiated each of the control codes so they could easily be told apart would be great, but WYSIWYG is something for end users, not people writing code.
Consider some simple situations:
echo -a $replace(04,)
echo -a $replace(,)
echo -a 2hello, 1,0there
echo -a hello, there
echo -a 2hello, 1there
echo -a 2hello, there
var %warn = 04 | echo -a %warn $+ DANGER!: This isn't coloured properly!
var %warn = | echo -a %warn $+ DANGER!: This isn't coloured properly!
There are obviously thousands of variations on these, but I think you get the picture. WYSIWYG doesn't work in code where the formatting could be coming from any number of places besides being literally inputted into the script, and can cause a lot of headaches for a scripter if he's getting a bug because of characters he can't even see.