MS Chat is the one that's bastardized the IRC protocol and ruined it's implementation of it.
IRC is a line-by-line chat protocol. You cannot put any newlines or carriage returns in it.
If you want an MS Chat compatability script, it's going to strip out the MS Chat uniqueness, and make it more flat IRC.
I've never seen or heard of anyone trying to make mIRC more like 'MS Chat'.