Right. The /parseline -u switch is actually doing the right thing here. The -u switch is not for how the binary variable is handled, it is for enabling/disabling UTF-8 parsing in the core server send/receive routines.
Binary variables, on the other hand, are automatically UTF-8 encoded/decoded in some contexts. They were implemented in this way for historical reasons, ie. to maintain backward compatibility with pre-Unicode versions of mIRC.
That said, some years ago I added an undocumented -a switch to /parseline which looks like it should do what you want, ie. treats the characters in the binary variable as non-UTF-8.
