It surprises me that Adobe Illustrator (mine is 15.1, a.k.a. CS5.1) doesn’t respect figure space. A figure space (which I would prefer to call digit space or numeral space) has the same width as the digit zero, but (obviously!) makes no mark on the page. Most typefaces (“fonts”) have digits that set to the same width, and in those typefaces the figure space is very useful to align numbers.
FIGURE SPACE is defined in Unicode as U+2007. In this notation, 2007 is the hexadecimal form of the Unicode code point. Inserting this character into an Illustrator file produces a space, but not of the same width as a digit.
You can work around the issue in Illustrator by using the digit zero, but using stroke None and fill None so as to make no mark.
By the way, you can enter Unicode characters directly in most Mac applications by choosing the Unicode Hex Input source. Access System Preferences → Keyboard, choose the Keyboard tab, and enable Show Keyboard & Character Viewers in menu bar. Then access Input Sources (also available from the Language & Text preference panel), scroll to the bottom, and enable Unicode Hex Input.
Upon closing the preferences panel, you’ll see a flag (Canadian, in my case) at the right-hand side of the menu bar. That’s a pull-down menu, one of whose choices is Unicode Hex Input. Once you choose that input source, you can enter a Unicode character by holding Option down continuously while you key four hex characters (0–9 and a–f or A–F). Obviously, normal entry of text is impaired when this input source is selected – for example, é, e-acute, can’t be entered directly. I recommend that you choose your normal source as soon immediately after entering Unicode.
By the way, if you see the term font designer in a document, in my view that document cannot be definitive on typesetting. The person to whom that document refers is known in the profession as a typeface designer.