Actually, your right about spaces.dll, I use it in my Mudclient script to force support for multiple spaces in my custom windows
As for $chr(160), they're right, it's not a space characters and on some fonts (so far I've only seen this with Terminal), it shows up as a block. Personally, I haven't experienced it with any of the fonts I use, so I use it as a black characters with my scripts. Down to preference really.
Btw thanks for the undocumented identifiers, now I have something new to play with!