On Stack Overflow, a version tag (e.g. "c#-4.0") is used when the question is about a feature specific for that version.
Is the same true for the OS tags used on Ask Different, or should I use the OS tags only to report the OS I am using?
Our version-specific OS tags use the 'big cat' name of the OS release.
Use one of these when you have a question that's OS-specific.
Tags should not be used just to tell us what version of the OS you're using; add that to the question itself.
"How can I rename Desktops in Lion?"
"Error when connecting to my Mac with SSH"