css1 namespace

Why is the yen sign allowed as a character in an ID name under CSS1 
-- but not the dollar sign?

Why is the paragraph sign allowed as a character in an ID name, but not
the '.' dot?

Why would the registered trademark sign be allowed, but not underscore?

I imagine the reasoning behind this strange exclusion and inclusion was
simplification of reference to the "second half" of the Latin-1
set and not more than that.

Anyone else interested in changing the set that is implemented to
underscore?   Without escaping it?

Donna Converse