mirc does parse ANSI codes, but only from incoming messages, not with /echo for example.
//.notice $me $chr(27) $+ [1mhello
result: -qwerty- hello
//echo -a $chr(27) $+ [1mhello
result: [1mhello
You can always use $ansi2mirc() though: //echo -a $ansi2mirc($chr(27) $+ [1mhello)
A suggestion could be a new switch for /echo that makes it interpret ANSI codes (-o maybe?)