I'm not a script programmer, I'm a user. I have no intention of intercepting every message to and from all servers, comparing them to known channels and usernames that should use a particular encoding, and then running a codepage conversion function on them, in mircscript.

Since mirc already has the required conversion system coded into it - just at a different location than would be functionally useful - adding a userfriendly SJIS/JIS variable to mirc windows would have preference over scripting something, as it would be less prone to bugs on the side of whoever tries to make the scripts as suggested, and doesn't require users to load all kinds of scripts from non-official sources, but can just select the option from the window options under the window icon like we can now for the window buffer, font, logging option, etc.

Please bear in mind that I am not recommending this feature because I'm the only one in need of it. (If I was, I might actually have already done what you suggested, though I don't quite like the idea of intecepting data before mirc is supposed to handle it). Rather, I'm asking this for at least fifty people I know, and a few thousand others at the least that can't be bothered to actually write a message on the official mirc board, but yak on about it in random channels that are in or about Japanese, when the issue of Japanese support (and not so much unicode in general but specifically the SJIS/JIS conversion setup as it exists currently) in mIRC is raised.