@WorldDMT, many months too late I know:
I tested this situation you describe. When I input 444 on CHR to ASC mode, I just receive the code for the first digit (52), which would be the $asc(4) result.
When I input 444 in ASC to CHR mode, I receive Ƽ. Look real close, it looks like a five but it's different. I believe it's because of mIRC's support for Unicode, starting with v7.1.