As far as your history link, it sounds more like ircle's author is whining about not having his method become standard instead of mIRC's. He's even suggesting fewer colors with a single digit fixed width color standard (0-9). Yes, he does offer a variable width option, but requires even more characters by requiring the use of []'s, which as far as I'm concerned looks bad and isn't nearly as quick to type.
You are misunderstanding his proposal. His proposal does not require that colors be assigned to the ASCII digits 0-9. Instead the byte following the control code can be any ASCII character which would allow for hundreds of colors. I'm not saying I agree with that design, but just clarifying what he meant.
Also, the brackets [] are just indicating that a second byte is optional. You aren't actually typing out those characters.
Personally, I like the way the current implementation uses written numbers because it is a lot more intuitive to users who don't understand what is going on under the hood. The only thing I would change would be possibly adding another 16 or so colors using the current system.
