mIRC does support utf-8 in many places.
You must have incorrect client settings, because the channel you're referring to shows up fine for me:
så va de
överhettad 24/7
etc.
All show up just fine.
Now if you're talking about the topic in the titlebar only, that is a
known bug and Khaled is hopefully working on it for the next release. It likely won't be fixed soon though, as it has to do with mIRC not being a natively unicode application, which it won't be for a while. To say mIRC doesn't support utf-8, though, is mostly false. It supports utf-8 for the most part but still has some outlying issues.
Otherwise, if you're talking about the text in the channel, you need to enable multibyte editbox, multibyte display, utf-8 display and font linking in Alt+O -> IRC -> Messages to get UTF-8 working right, and then you need to (IMPORTANT!)
select a font that supports UTF-8 and choose "Display and Encode" in the UTF8 dropdown to be able to write UTF-8 to the channel.
I'm not sure what the problem is here, why a script is necessary? I really think this is just a case of misconfiguring mIRC.
On a sidenote, the link to that blog post and script is 4 years old. mIRC has progressed considerably since then, the functionality within that script
has been implemented, and both the contents of the post and that script are now invalid/obsolete.
