As far as the spaces problem goes - indeed, your script uses the common double-bold trick; other scripts use $chr(160) and I've written a
dll that can use real spaces in output, but personally, I'd much rather see
proper script support for multiple consecutive spaces. That will fix all such problems, and many more.
However, even if that were actually added, I still agree with the original poster that a built-in customization feature for the nick tags would be nice, because of the sheer number of people asking for this. On the other hand, if there's an option to change that part of the default output, there's the risk that people will be asking for more and more options to change other parts of the default output as well. And I'm not sure it's mIRC's job to ultimately provide a complete built-in theming system, if it can also be scripted...