3. Using HTML syntax to declare control codes means you can't use those same HTML codes in a message unless mIRC creates some magical way to escape HTML syntax, which would lead to all around ugliness. Its probable that someone would want to send a message including the literal "<color>" tag. Control codes on the other hand are out of the printable range, so can reasonably expect that they are not part of any IRC message.
Wait... you seriously think that you can apply a color code change with PUBLIC messages? Umm... no... too late. This is solely for local displaying. This would only apply to local echo commands. You make *any* change to the existing public IRC standard and everyone and they're mother will have a major fit. It's not mIRC's decision to make anymore. You want color changes, they are ONLY going to apply to local displayed messages.
/echo
<COLOR="Info Text"/> -a
<COLOR="RED"/>Hello
<COLOR="FFFFFF"/>World
<COLOR="BLUE"/>!
That's not as ugly as it is now...
