Deriving authority for this statement form Eric Meyer is misleading. Eric didn't say don't use outline: none, he said make sure you have focus styles.
Browser defaults are ugly and inconsistent. Ordering designers everywhere to not override that is like telling Picasso to paint realistically because some people find his work inaccessible.
Asking designers nicely to make sure they have elegant focus styles is both appealing to their ability and sensibility without insulting their creativity.
The difference is negligible. Complexity of grammar (not the same thing) is probably the big cost factor. The big thing there is usually ambiguity of a statement within a single context that has to be resolved. Static is not such a case because there are three distinct contexts. But when a parser has to read many tokens ahead just to figure out where you're going with a term, that's what slows things down.
At least the third meaning is deprecated in favor of anonymous namespaces.
The other two are essentially the same just within class or function scope. Of course, they're essentially just global state of a sort, but they sure do come in useful at times.
Browser defaults are ugly and inconsistent. Ordering designers everywhere to not override that is like telling Picasso to paint realistically because some people find his work inaccessible.
Asking designers nicely to make sure they have elegant focus styles is both appealing to their ability and sensibility without insulting their creativity.