Let's get our stuff straight.

I'm running a clean installation of mIRC, and I'm simply typing /msg someone something with spaces.

I am not using any scripts.

I know it handles incomming messages correctly, but that has nothing to do with the point.

It also has a fine calculator and I also think it has a channel list. But that too is irelevant, so let's stick to the point.

The point being.
I can start telnet and message my friend somethign with spaces.

I can't do this with mIRC unless I first open a window with him and then type in that window. Ie. I can't just use the /msg command.