Out of all the encoded fixed-width spaces, this is the one whose purpose completely eludes me.
The Unicode Standard defines it thus: “U+2008 punctuation space is a space defined to be the same width as a period.” [Version 8.0 p. 266]
I have seen Adobe documentation
about their Insert White Space > Punctuation Space (which does indeed insert the U+2008 codepoint) described as “Same width as an exclamation point, period, or colon in the typeface” — which is, of course, somewhat arbitrary, given that in any given font those three punctuation marks are not necessarily going to have the same advance width.
Does anyone know precisely why the Unicode Consortium chose to encode this space and what the proposed usage was that made this a convincing case for inclusion?
I have my own thoughts about what such a space could/should actually be useful for, practically speaking; but they don’t necessarily coincide with the minimal definition, and I have no reason to believe that others would expect it to be designed for such usage.