You seem to go about CSS very differently then most. The typical way of doing styleshets is more or less "What properties does this type of element have? Now what about this type?..." Rather than "Now which elements on my site have this property-value? What about this property-value?..."
Which isn't to say that comma syntax is in any way rare, just that CSS is usually approached by pairing properties to selectors, not the other way around. I would say this helps your style sheet make intuitive sense too. If you want to change the color of the sidebar text, you find the part of your style sheet for #sidebar and then change the color property, rather than finding the section for "blue", removing the sidebar from a big comma separated list of selectors, then placing it into a similar list for "green".
From this standpoint variables make a lot of sense.
Which isn't to say that comma syntax is in any way rare, just that CSS is usually approached by pairing properties to selectors, not the other way around. I would say this helps your style sheet make intuitive sense too. If you want to change the color of the sidebar text, you find the part of your style sheet for #sidebar and then change the color property, rather than finding the section for "blue", removing the sidebar from a big comma separated list of selectors, then placing it into a similar list for "green".
From this standpoint variables make a lot of sense.