It turns out that the "Command Key" symbol is typed using the 'z' character and changed to Wingdings font. My understanding is that this font is including (only) on Microsoft Windows. So, the Mac users whom this is aimed at will see a 'z' instead, or perhaps something goofy as it gets substituted with some random symbol font. Is it actually visible on people's Mac's?
The character ⌘ displays correctly for me. I disabled Wingdings and it still displays. There are several fonts included with Macs that include it.
The character '⌘' encoded as U+2318. I see that it is not present in the Liberation fonts used by the main text, but it shows up anyway in the document. I presume this is some kind of font fall-back ability. So, at least using the standard Unicode character will show up even if the needed font is absent! And what font to use?
A long as ⌘ is encoded as U+2318 it will be displayed on a Mac.
Larry